Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 51,085	$ (93,268)	$ 134,158
Other comprehensive income (loss):
Foreign currency translation adjustments	(453)	3,510	96
Income tax benefit (expense)	296	(531)	(243)
Foreign currency translation adjustments, net of tax	(157)	2,979	(147)
Unrealized gains on investments:
Unrealized gains arising during period	516	73	257
Less: reclassification adjustments for gains (losses) included in net income	17	(13)	19
Change in unrealized gains on investments	499	86	238
Income tax (expense) benefit	(242)	62	(99)
Unrealized gains on investments, net of tax	257	148	139
Changes in employee benefit related items:
Amortization of transition asset	(54)	(53)	(49)
Amortization of prior service cost	40	40	(316)
Recognized actuarial loss (gain)	(3,792)	(5,791)	(3,585)
Changes in employee benefit related items	(3,806)	(5,804)	(3,950)
Income tax (expense) benefit	(50)	128	46
Employee benefit related items, net of tax	(3,856)	(5,676)	(3,904)
Other comprehensive income (loss)	(3,756)	(2,549)	(3,912)
Comprehensive income (loss)	$ 47,329	$ (95,817)	$ 130,246