Stockholders' Equity (Changes in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amount, beginning balance			$ 3,561,931	$ 3,201,888
Other comprehensive (loss) income before reclassifications			73,056	(41,318)
Amounts reclassified from accumulated other comprehensive loss (income)	$ (51,477)	$ 451	(51,890)	(1,114)
Other comprehensive (loss) income	(26,025)	(1,941)	21,166	(42,432)
Amount, ending balance	3,824,137	3,519,838	3,824,137	3,519,838
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amount, beginning balance			(129,292)	(79,433)
Amount, ending balance	(108,126)	(121,865)	(108,126)	(121,865)
Benefits Liability, Net of Tax [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amount, beginning balance			(8,607)	(23,442)
Other comprehensive (loss) income before reclassifications			(252)	(128)
Amounts reclassified from accumulated other comprehensive loss (income)	228	451	661	1,318
Other comprehensive (loss) income			409	1,190
Amount, ending balance	(8,198)	(22,252)	(8,198)	(22,252)
Cumulative Foreign Currency Exchange, Net of Tax [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amount, beginning balance			(115,690)	(56,224)
Other comprehensive (loss) income before reclassifications			15,758	(43,746)
Amounts reclassified from accumulated other comprehensive loss (income)			0	0
Other comprehensive (loss) income			15,758	(43,746)
Amount, ending balance	(99,932)	(99,970)	(99,932)	(99,970)
Net Unrealized Holdings Gains (Losses) on Investments, Net of Tax [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amount, beginning balance			(4,995)	233
Other comprehensive (loss) income before reclassifications			57,550	2,556
Amounts reclassified from accumulated other comprehensive loss (income)			(52,551)	(2,432)
Other comprehensive (loss) income			4,999	124
Amount, ending balance	$ 4	$ 357	$ 4	$ 357