Stockholders' Equity (Changes in Stockholders' Equity) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			$ 3,561,931	$ 3,201,888
Net income	$ 115,620	$ 210,061	244,556	360,468
Pension and other post- retirement benefits liability			306	752
Foreign currency translation adjustments			9,305	(41,826)
Net unrealized holding gains on investments			37,580	583
Common stock repurchased			(66,725)	(62,804)
Shares issued—stock- based compensation			481	831
Stock-based compensation, net of tax on stock options exercised			5,403	6,800
Dividends paid			(47,317)	(43,896)
Distributions to noncontrolling interests			(8,084)	(7,218)
Noncontrolling interest in acquired business				1,597
Amount, ending balance	3,737,436	3,417,175	3,737,436	3,417,175
Common Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			1,347	1,347
Shares issued—stock- based compensation			0	0
Amount, ending balance	1,347	1,347	1,347	1,347
Treasury Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			(258,312)	(96,372)
Common stock repurchased			(66,725)	(62,804)
Shares issued—stock- based compensation			2,235	704
Amount, ending balance	(322,802)	(158,472)	(322,802)	(158,472)
Additional Paid-in Capital [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			542,148	530,441
Shares issued—stock- based compensation			(1,754)	127
Stock-based compensation, net of tax on stock options exercised			5,403	6,800
Amount, ending balance	545,797	537,368	545,797	537,368
Retained Earnings [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			3,109,987	2,555,528
Net income			234,252	351,437
Dividends paid			(47,317)	(43,896)
Amount, ending balance	3,296,922	2,863,069	3,296,922	2,863,069
Accumulated Other Comprehensive Income (Loss)
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			(129,292)	(79,433)
Pension and other post- retirement benefits liability			306	752
Foreign currency translation adjustments			9,305	(41,826)
Net unrealized holding gains on investments			37,580	583
Amount, ending balance	(82,101)	(119,924)	(82,101)	(119,924)
Noncontrolling Interest [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance			296,053	290,377
Net income			10,304	9,031
Distributions to noncontrolling interests			(8,084)	(7,218)
Noncontrolling interest in acquired business				1,597
Amount, ending balance	$ 298,273	$ 293,787	$ 298,273	$ 293,787