Stockholders' Equity (Changes in Stockholders' Equity) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amount, beginning balance			$ 3,561,931	$ 3,201,888
Net income	$ 70,014	$ 188,420	314,570	548,888
Pension and other post- retirement benefits liability			409	1,190
Foreign currency translation adjustments			15,758	(43,746)
Net unrealized holding gains on investments			4,999	124
Common stock repurchased			(66,725)	(122,249)
Shares issued—stock- based compensation			1,650	984
Stock-based compensation, net of tax on stock options exercised			7,778	9,996
Dividends paid			(71,933)	(67,852)
Distributions to noncontrolling interests			(12,300)	(10,982)
Noncontrolling interest in acquired business			68,000	1,597
Amount, ending balance	3,824,137	3,519,838	3,824,137	3,519,838
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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
Common Stock, Held in Treasury [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amount, beginning balance			(258,312)	(96,372)
Common stock repurchased			(66,725)	(122,249)
Shares issued—stock- based compensation			5,057	1,079
Amount, ending balance	(319,980)	(217,542)	(319,980)	(217,542)
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amount, beginning balance			542,148	530,441
Shares issued—stock- based compensation			(3,407)	(95)
Stock-based compensation, net of tax on stock options exercised			7,778	9,996
Amount, ending balance	546,519	540,342	546,519	540,342
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amount, beginning balance			3,109,987	2,555,528
Net income			299,914	535,041
Dividends paid			(71,933)	(67,852)
Amount, ending balance	3,337,968	3,022,717	3,337,968	3,022,717
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amount, beginning balance			(129,292)	(79,433)
Pension and other post- retirement benefits liability			409	1,190
Foreign currency translation adjustments			15,758	(43,746)
Net unrealized holding gains on investments			4,999	124
Amount, ending balance	(108,126)	(121,865)	(108,126)	(121,865)
Noncontrolling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amount, beginning balance			296,053	290,377
Net income			14,656	13,847
Distributions to noncontrolling interests			(12,300)	(10,982)
Noncontrolling interest in acquired business			68,000	1,597
Amount, ending balance	$ 366,409	$ 294,839	$ 366,409	$ 294,839