Summary of Significant Accounting Policies - Accounting for Employee Share-Based Payment (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income before income taxes	$ 170,204	$ 162,348	$ 156,912	$ 165,357	$ 319,260	$ 489,464	$ 450,296
Provision for income taxes	40,586	46,095	45,822	48,587	91,917	132,503	140,695
Net income	$ 129,618	$ 116,253	$ 111,090	$ 116,770	$ 227,343	$ 356,961	$ 309,601
Earnings per share:
Basic earnings per share (in dollars per share)	$ 1.40	$ 1.25	$ 1.20	$ 1.27	$ 2.46	$ 3.85	$ 3.37
Diluted earnings per share (in dollars per share)	$ 1.36	$ 1.22	$ 1.17	$ 1.24	$ 2.39	$ 3.75	$ 3.29
Weighted average shares outstanding:
Basic weighted average shares outstanding (in shares)	92,631	92,665	92,516	92,110	92,591	92,604	91,923
Diluted weighted average shares outstanding (in shares)	95,307	95,279	95,030	94,157	95,137	95,204	94,069
Net cash provided by operating activities		$ 212,042	$ 122,623			$ 404,286	$ 524,452
Net cash used in investing activities		(37,924)	(20,745)			(1,371,545)	(46,547)
Net cash used in financing activities		(121,489)	(158,507)			976,413	(502,264)
Effect of foreign currency exchange rates on cash		(6,696)	8,795			(50,871)	(30,320)
Net decrease in cash and cash equivalents		45,933	(47,834)			$ (41,717)	$ (54,679)
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income before income taxes		162,348	156,912		$ 319,260
Provision for income taxes		48,163	46,940		95,103
Net income		$ 114,185	$ 109,972		$ 224,157
Earnings per share:
Basic earnings per share (in dollars per share)		$ 1.23	$ 1.19		$ 2.42
Diluted earnings per share (in dollars per share)		$ 1.21	$ 1.17		$ 2.37
Weighted average shares outstanding:
Basic weighted average shares outstanding (in shares)		92,665	92,516		92,591
Diluted weighted average shares outstanding (in shares)		94,549	94,329		94,433
Net cash provided by operating activities		$ 208,856	$ 121,505
Net cash used in investing activities		(37,924)	(20,745)
Net cash used in financing activities		(118,303)	(157,389)
Effect of foreign currency exchange rates on cash		(6,696)	8,795
Net decrease in cash and cash equivalents		45,933	(47,834)
Adjustments | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income before income taxes		0	0		$ 0
Provision for income taxes		(2,068)	(1,118)		(3,186)
Net income		$ 2,068	$ 1,118		$ 3,186
Earnings per share:
Basic earnings per share (in dollars per share)		$ 0.02	$ 0.01		$ 0.04
Diluted earnings per share (in dollars per share)		$ 0.01	$ 0.00		$ 0.02
Weighted average shares outstanding:
Basic weighted average shares outstanding (in shares)		0	0		0
Diluted weighted average shares outstanding (in shares)		729	701		703
Net cash provided by operating activities		$ 3,186	$ 1,118
Net cash used in investing activities		0	0
Net cash used in financing activities		(3,186)	(1,118)
Effect of foreign currency exchange rates on cash		0	0
Net decrease in cash and cash equivalents		$ 0	$ 0