Income Taxes - Effective Income Tax Rate Reconciliation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Computed federal income tax expense at statutory rate of 35%									$ 6,943	$ 9,667	$ 11,506
State income taxes									397	436	699
Tax credits									(1,385)	(779)	(778)
Production activity deduction									0	(388)	(425)
Foreign tax rate differential									(2,374)	(1,419)	(1,297)
Uncertain tax positions									(520)	(42)	281
Deferred compensation insurance assets									(358)	(155)	88
Other — including the effect of graduated rates									566	588	(243)
Total	$ 1,642	$ 833	$ 1,253	$ (459)	$ 1,209	$ 1,811	$ 2,719	$ 2,169	$ 3,269	$ 7,908	$ 9,831