Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Statement of Stockholders' Equity [Abstract]
Net income	$ 86,964	$ 67,930	$ 290,278	$ 232,523
Pension and other post-retirement benefits liability
Pension and other post-retirement reserves adjustment (excluding amortization)	72	0	142	0
Amortization of benefits liability	584	471	1,747	1,395
Income tax provision on pension and other post-retirement benefits liability	(252)	(185)	(725)	(548)
Foreign currency translation adjustments	865	(1,054)	928	(730)
Reclassification of net cash flow hedge losses to net income	521	0	0	0
Available-for-sale investments
Unrealized holding gains (losses) on investments	339	(6,659)	14,582	(6,659)
Income tax provision on unrealized holding gains	(121)	0	(5,229)	0
Reclassification of net realized gain to net income	(306)	0	(10,538)	0
Other comprehensive income (loss)	1,702	(7,427)	907	(6,542)
Comprehensive income	$ 88,666	$ 60,503	$ 291,185	$ 225,981