Annual report pursuant to Section 13 and 15(d)

INVESTMENT SECURITIES (Details 2)

v2.4.1.9
INVESTMENT SECURITIES (Details 2) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Trading securities portfolio      
Trading securities portfolio $ 1,038us-gaap_TradingSecuritiesRestricted $ 971us-gaap_TradingSecuritiesRestricted  
Gains 56us-gaap_TradingSecuritiesRealizedGain 122us-gaap_TradingSecuritiesRealizedGain 116us-gaap_TradingSecuritiesRealizedGain
U.S. government security funds      
Trading securities portfolio      
Net Unrealized Losses $ 15natr_AvailableForSaleSecuritiesNetUnrealizedLosses
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentDebtSecuritiesMember
$ 14natr_AvailableForSaleSecuritiesNetUnrealizedLosses
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentDebtSecuritiesMember