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Investments In Marketable Securities (Narrative) (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Marketable Securities [Abstract]      
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax $ 11,415us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax $ 8,562us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax  
Dividend Income On Marketable Securities $ 716nhi_DividendIncomeOnMarketableSecurities $ 667nhi_DividendIncomeOnMarketableSecurities $ 628nhi_DividendIncomeOnMarketableSecurities