Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net gain (loss) arising during the period, Tax	$ 21,424	$ (5,968)	$ (21,960)
Prior service (cost) credit arising during the period, tax	0	2,159	2,264
Amortization of actuarial loss included in net periodic cost, tax	9,024	7,208	5,414
Amortization of prior service credit included in net periodic cost, tax	$ (3,482)	$ (3,343)	$ (3,062)