Condensed Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Tax expense recognized on the amortization of prior service cost	$ (6)	$ (6)	$ (18)	$ (19)
Tax expense recognized on the net gain (loss)	$ (43)	$ (51)	$ (124)	$ (152)