Unaudited Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total		Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Stockholders' Equity beginning balance at Dec. 31, 2017		$ 3,676,522		$ 122	$ 2,214,224	$ 2,958,921	$ (551,857)	$ (944,888)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		174,937				174,937
Other comprehensive income from currency, net of tax		43,254					43,254
Acquisition of common stock		(88,292)						(88,292)
Share-based compensation		14,403			14,403
Issuance of common stock		19,976		1	19,975
Stockholders' Equity ending balance at Mar. 31, 2018		3,888,052		123	2,248,602	3,181,110	(508,603)	(1,033,180)
Stockholders' Equity beginning balance at Dec. 31, 2017		3,676,522		122	2,214,224	2,958,921	(551,857)	(944,888)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	[1]	509,483
Stockholders' Equity ending balance at Sep. 30, 2018		3,562,247		123	2,316,753	3,515,656	(944,746)	(1,325,539)
Stockholders' Equity beginning balance at Mar. 31, 2018		3,888,052		123	2,248,602	3,181,110	(508,603)	(1,033,180)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		176,852				176,852
Other comprehensive income from currency, net of tax		(362,085)					(362,085)
Acquisition of common stock		(292,359)						(292,359)
Share-based compensation		19,102			19,102
Issuance of common stock		9,523			9,523
Stockholders' Equity ending balance at Jun. 30, 2018		3,439,085		123	2,277,227	3,357,962	(870,688)	(1,325,539)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		157,694	[1]			157,694
Other comprehensive income from currency, net of tax		(74,058)					(74,058)
Acquisition of common stock		0						0
Share-based compensation		20,702			20,702
Issuance of common stock		18,824			18,824
Stockholders' Equity ending balance at Sep. 30, 2018		3,562,247		123	2,316,753	3,515,656	(944,746)	(1,325,539)
Stockholders' Equity beginning balance at Dec. 31, 2018		3,340,180		123	2,306,843	3,817,656	(913,858)	(1,870,584)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		172,107				172,107
Other comprehensive income from currency, net of tax		(20,334)					(20,334)
Acquisition of common stock		(3,322)			33,000			(36,322)
Share-based compensation		12,541			12,541
Issuance of common stock		29,795			29,795
Stockholders' Equity ending balance at Mar. 31, 2019		3,530,967		123	2,382,179	3,989,763	(934,192)	(1,906,906)
Stockholders' Equity beginning balance at Dec. 31, 2018		3,340,180		123	2,306,843	3,817,656	(913,858)	(1,870,584)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	[2]	659,563
Stockholders' Equity ending balance at Sep. 30, 2019		3,900,310	[3]	123	2,503,590	4,477,219	(1,114,678)	(1,965,944)
Stockholders' Equity beginning balance at Mar. 31, 2019		3,530,967		123	2,382,179	3,989,763	(934,192)	(1,906,906)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		261,651				261,651
Other comprehensive income from currency, net of tax		5,995					5,995
Acquisition of common stock		(702)						(702)
Share-based compensation		18,306			18,306
Issuance of common stock		27,155			27,155
Stockholders' Equity ending balance at Jun. 30, 2019		3,843,372		123	2,427,640	4,251,414	(928,197)	(1,907,608)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		225,805				225,805
Other comprehensive income from currency, net of tax		(186,481)					(186,481)
Acquisition of common stock		(58,336)						(58,336)
Share-based compensation		15,273			15,273
Issuance of common stock		60,677			60,677
Stockholders' Equity ending balance at Sep. 30, 2019		$ 3,900,310	[3]	$ 123	$ 2,503,590	$ 4,477,219	$ (1,114,678)	$ (1,965,944)

[1] Reflects reclassifications from previously disclosed amounts to conform to current presentation.

[2] Reflects the impact of the Company's adoption of ASU 2016-02 "Leases", on January 1, 2019, using the modified retrospective transition method. Under this method, financial results reported in periods prior to 2019 are unchanged. Refer to footnote 2.

[3] Reflects the impact of the Company's adoption of ASU 2016-02 "Leases", on January 1, 2019, using a modified retrospective transition method. Under this method, financial results reported in periods prior to 2019 are unchanged. Refer to footnote 2.