Condensed Statements of Comprehensive Income (unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Condensed Statements of Comprehensive Income (unaudited) [Abstract]
Net income	$ 40,276	$ 21,339	$ 78,507	$ 48,038
Other comprehensive income (loss):
Foreign currency translation adjustments	(3,112)	(1,412)	(6,990)	(729)
Income tax (expense) benefit	(6)	296	(12)	296
Foreign currency translation adjustments, net of tax	(3,118)	(1,116)	(7,002)	(433)
Unrealized (losses) gains on investments:
Unrealized (losses) gains arising during period	(161)	26	121	290
Less: reclassification adjustments for gains included in net income	3	7	3	7
Changes in unrealized (losses) gains on investments	(164)	19	118	283
Income tax benefit (expense)	22	(10)	(123)	(123)
Unrealized gains on investments, net of tax	(142)	9	(5)	160
Changes in employee benefit related items:
Amortization of transition asset	(5)	(14)	(18)	(27)
Amortization of prior service cost	10	10	19	20
Recognized actuarial loss	69	74	136	45
Changes in employee benefit related items	74	70	137	38
Income tax (expense)	(1)	(1)	(36)	(1)
Employee benefit related items, net of tax	73	69	101	37
Other comprehensive income (loss)	(3,187)	(1,038)	(6,906)	(236)
Comprehensive income	$ 37,089	$ 20,301	$ 71,601	$ 47,802