Stockholders' Equity (Changes in Stockholders' Equity) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			$ 3,201,888	$ 2,418,603
Net income	$ 210,061	$ 169,443	360,468	327,475
Pension and other post- retirement benefits liability			752	255
Foreign currency translation adjustments			(41,826)	(90)
Net unrealized holding gains on investments			583	2,319
Common stock repurchased			(62,804)
Shares issued—stock- based compensation			831	4,187
Stock-based compensation, net of tax on stock options exercised			6,800	8,947
Dividends paid			(43,896)	(33,623)
Distributions to noncontrolling interests			(7,218)
Noncontrolling interest in acquired business			1,597
Amount, ending balance	3,417,175	2,728,073	3,417,175	2,728,073
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	1,347	1,347
Treasury Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			(96,372)	(46,220)
Common stock repurchased			(62,804)
Shares issued—stock- based compensation			704	1,039
Amount, ending balance	(158,472)	(45,181)	(158,472)	(45,181)
Additional Paid-in Capital [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			530,441	511,432
Shares issued—stock- based compensation			127	3,147
Stock-based compensation, net of tax on stock options exercised			6,800	8,947
Amount, ending balance	537,368	523,526	537,368	523,526
Retained Earnings [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			2,555,528	1,954,661
Net income			351,437	327,475
Dividends paid			(43,896)	(33,623)
Amount, ending balance	2,863,069	2,248,513	2,863,069	2,248,513
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			752	255
Foreign currency translation adjustments			(41,826)	(90)
Net unrealized holding gains on investments			583	2,319
Amount, ending balance	(119,924)	$ (132)	(119,924)	$ (132)
Noncontrolling Interest [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			290,377
Net income			9,031
Distributions to noncontrolling interests			(7,218)
Noncontrolling interest in acquired business			1,597
Amount, ending balance	$ 293,787		$ 293,787