Income Taxes - Effective Income Tax Reconciliation (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate		35.00%
United States		$ 115,850	$ 235,256	$ 281,579
International		578,438	480,141	410,604
Income before income taxes		694,288	715,397	692,183
Provision at statutory tax rate		243,001	250,389	242,264
State taxes, net of federal benefit		5,184	9,219	10,526
International effective tax rate differential		(88,444)	(64,002)	(56,132)
Change in valuation allowance		1,408	7,174	(205)
Other non-deductible expenses		12,700	3,516	3,530
Changes in tax accruals		(7,973)	(3,679)	(7,423)
Tax Credits		(8,170)	(14,510)	0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	[1]	(71,261)
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	[2]	196,010	0	0
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount			0	0
Other		4,671	2,567	(863)
Provision for income taxes		$ 287,126	$ 190,674	$ 191,697

[1] For the year ended December 31, 2017, the company accrued $71,261 in provisional tax benefit related to the net change in deferred tax liabilities stemming from the Tax Act’s reduction of the U.S. federal tax rate from 35% to 21%, and disallowance of certain incentive based compensation tax deductibility under Internal Revenue Code Section 162(m).

[2] For the year ended December 31, 2017, the company accrued a reasonable estimate of $196,010 of tax expense for the Tax Act’s one-time transition tax on the foreign subsidiaries’ accumulated, unremitted earnings going back to 1986