| Summary of Significant Accounting Policies (Details) (USD $)Share data in Thousands, except Per Share data, unless otherwise specified
 | 3 Months Ended | 12 Months Ended | 
      
        | Dec. 27, 2014 | Sep. 27, 2014 | Jun. 28, 2014 | Mar. 29, 2014 | Dec. 28, 2013 | Sep. 28, 2013 | Jun. 29, 2013 | Mar. 30, 2013 | Dec. 27, 2014 | Dec. 28, 2013 | Dec. 29, 2012 | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Reinsurance Purchased For Stop Losses On Individual Basis |  |  |  |  |  |  |  |  | $ 155snhy_ReinsurancePurchasedForStopLossesOnIndividualBasis |  |  | 
      
        | Computation of basic and diluted earnings per common share |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Net income | 10,327,000us-gaap_NetIncomeLoss | 9,877,000us-gaap_NetIncomeLoss | 12,186,000us-gaap_NetIncomeLoss | 11,385,000us-gaap_NetIncomeLoss | 8,343,000us-gaap_NetIncomeLoss | 8,275,000us-gaap_NetIncomeLoss | 11,790,000us-gaap_NetIncomeLoss | 9,575,000us-gaap_NetIncomeLoss | 43,775,000us-gaap_NetIncomeLoss | 37,984,000us-gaap_NetIncomeLoss | 37,398,000us-gaap_NetIncomeLoss | 
      
        | Weighted average basic shares outstanding |  |  |  |  |  |  |  |  | 26,456us-gaap_WeightedAverageNumberOfSharesOutstandingBasic | 26,206us-gaap_WeightedAverageNumberOfSharesOutstandingBasic | 25,944us-gaap_WeightedAverageNumberOfSharesOutstandingBasic | 
      
        | Basic net income per common share (in dollars per share) | $ 0.39us-gaap_EarningsPerShareBasic | $ 0.37us-gaap_EarningsPerShareBasic | $ 0.46us-gaap_EarningsPerShareBasic | $ 0.43us-gaap_EarningsPerShareBasic | $ 0.32us-gaap_EarningsPerShareBasic | $ 0.32us-gaap_EarningsPerShareBasic | $ 0.45us-gaap_EarningsPerShareBasic | $ 0.37us-gaap_EarningsPerShareBasic | $ 1.65us-gaap_EarningsPerShareBasic | $ 1.45us-gaap_EarningsPerShareBasic | $ 1.44us-gaap_EarningsPerShareBasic | 
      
        | Effect of dilutive stock options |  |  |  |  |  |  |  |  | 0us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements | 0us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements | 0us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements | 
      
        | Weighted average diluted shares outstanding |  |  |  |  |  |  |  |  | 26,456us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding | 26,206us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding | 25,971us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding | 
      
        | Diluted net income per common share (in dollars per share) | $ 0.39us-gaap_EarningsPerShareDiluted | $ 0.37us-gaap_EarningsPerShareDiluted | $ 0.46us-gaap_EarningsPerShareDiluted | $ 0.43us-gaap_EarningsPerShareDiluted | $ 0.32us-gaap_EarningsPerShareDiluted | $ 0.32us-gaap_EarningsPerShareDiluted | $ 0.45us-gaap_EarningsPerShareDiluted | $ 0.37us-gaap_EarningsPerShareDiluted | $ 1.65us-gaap_EarningsPerShareDiluted | $ 1.45us-gaap_EarningsPerShareDiluted | $ 1.44us-gaap_EarningsPerShareDiluted | 
      
        | Reinsurance Purchased For Stop Losses on Aggregate Basis |  |  |  |  |  |  |  |  | $ 7,200snhy_ReinsurancePurchasedForStopLossesonAggregateBasis |  |  | 
      
        | Computer Equipment [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Estimated useful life |  |  |  |  |  |  |  |  | 3 years |  |  | 
      
        | Computer Equipment [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Estimated useful life |  |  |  |  |  |  |  |  | 5 years |  |  | 
      
        | Machinery and equipment | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Estimated useful life |  |  |  |  |  |  |  |  | 4 years |  |  | 
      
        | Machinery and equipment | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Estimated useful life |  |  |  |  |  |  |  |  | 12 years |  |  | 
      
        | Furniture and Fixtures [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Estimated useful life |  |  |  |  |  |  |  |  | 4 years |  |  | 
      
        | Furniture and Fixtures [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Estimated useful life |  |  |  |  |  |  |  |  | 10 years |  |  | 
      
        | Buildings | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Estimated useful life |  |  |  |  |  |  |  |  | 25 years |  |  | 
      
        | Buildings | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Estimated useful life |  |  |  |  |  |  |  |  | 40 years |  |  | 
      
        | Leasehold and land improvements | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Estimated useful life |  |  |  |  |  |  |  |  | 5 years |  |  | 
      
        | Leasehold and land improvements | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  | 
      
        | Estimated useful life |  |  |  |  |  |  |  |  | 15 years |  |  |