Stockholders' Equity (Changes in Stockholders' Equity) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2013
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	$ 3,201,888	$ 2,418,603
Net income	150,407	158,032
Pension and other post- retirement benefits liability	427	135
Foreign currency translation adjustments	(59,698)	(898)
Net unrealized holding gains on investments	1,042	1,597
Common stock repurchased	(2,000)
Shares issued—stock- based compensation	157	2,158
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	4,041	5,734
Dividends paid	(21,964)	(16,789)
Distributions to noncontrolling interests	(3,558)
Amount, ending balance	3,270,742	2,568,572
Common Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	1,347	1,346
Shares issued—stock- based compensation	0	1
Amount, ending balance	1,347	1,347
Treasury Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	(96,372)		(46,220)
Common stock repurchased	(2,000)
Shares issued—stock- based compensation	97
Amount, ending balance	(98,275)	(46,220)	(46,220)
Additional Paid-in Capital [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	530,441	511,432
Shares issued—stock- based compensation	60	2,157
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	4,041	5,734
Amount, ending balance	534,542	519,323
Retained Earnings [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	2,555,528	1,954,661
Net income	146,342	158,032
Dividends paid	(21,964)	(16,789)
Amount, ending balance	2,679,906	2,095,904
AOCI Attributable to Parent [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	(79,433)	(2,616)
Pension and other post- retirement benefits liability	427	135
Foreign currency translation adjustments	(59,698)	(898)
Net unrealized holding gains on investments	1,042	1,597
Amount, ending balance	(137,662)	(1,782)
Noncontrolling Interest [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	290,377
Net income	4,065
Distributions to noncontrolling interests	(3,558)
Amount, ending balance	$ 290,884