Condensed Statement of Comprehensive Income (unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Condensed Statement of Comprehensive Income (unaudited) [Abstract]
Net Income	$ 21,339	$ 35,512	$ 48,038	$ 79,192
Other comprehensive income (loss), before taxes:
Foreign currency translation adjustments	(1,412)	2,634	(729)	7,729
Unrealized gains on investments:
Unrealized gains arising during period	26	74	290	209
Less: reclassification adjustment for gains (losses) included in net income	7	1	7	(48)
Change in unrealized gains on investments	19	73	283	257
Changes in employee benefit related items:
Amortization of transition asset	(14)	(14)	(27)	(27)
Amortization of prior service cost	10	10	20	20
Recognized actuarial loss	74	40	45	20
Other comprehensive income (loss), before taxes	(1,323)	2,743	(408)	7,999
Income tax benefit (expense)	285	(160)	172	(261)
Comprehensive income	$ 20,301	$ 38,095	$ 47,802	$ 86,930