Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 170,290	$ 86,964	$ 439,453	$ 290,278
Pension and other post-retirement benefits liability
Pension and other post-retirement reserves adjustment (excluding amortization)	(489)	72	(978)	142
Amortization of benefits liability	695	584	2,004	1,747
Income tax provision on pension and other post-retirement benefits liability	(78)	(252)	(394)	(725)
Foreign currency translation adjustments	546	865	(844)	928
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0	521	0	0
Available-for-sale investments
Unrealized holding gains (losses) on investments	205	339	205	14,582
Income tax provision on unrealized holding gains	(74)	(121)	(74)	(5,229)
Reclassification of net realized gain to net income	0	(306)	0	(10,538)
Other comprehensive income (loss)	805	1,702	(81)	907
Comprehensive income	$ 171,095	$ 88,666	$ 439,372	$ 291,185