Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Tax expense recognized on the amortization of prior service cost	$ (7)	$ (6)	$ (14)	$ (12)
Tax expense recognized on the net gain (loss)	62	27	125	53
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	$ 4	$ (1)	$ 21	$ (1)