Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Comprehensive Income [Abstract]
Unrealized investment gains (losses) arising during the period, net of tax expense (benefit)	$ 96	$ 33	$ (36)
Amortization of net actuarial loss, net of tax expense (benefit)	2,380	(574)	(709)
Amortization of prior service credit, net of tax	$ (327)	$ (433)	$ (487)