Income Taxes - Summary of Provision for Income Taxes and U.S. Federal Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount [Abstract]
Computed “expected” tax expense	$ 48,141	$ 48,157
Foreign income tax differential	(4,692)	2,016
Excess tax benefit related to stock-based compensation	(6,385)	(4,624)
State taxes net of federal benefits	3,551	3,373
Foreign-sourced nontaxable income	(56)	(6,588)
Foreign tax credit/transition tax - federal only	5,275	5,471
GILTI, net of foreign tax credits	2,433	4,921
Change in valuation allowance	3,289	0
Other	5,578	1,656
Provision for income taxes	$ 57,134	$ 54,382
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Computed “expected” tax expense	21.00%	21.00%
Foreign income tax differential	(2.00%)	0.90%
Excess tax benefit related to stock-based compensation	(2.80%)	(2.00%)
State taxes net of federal benefits	1.50%	1.50%
Foreign-sourced nontaxable income	(0.00%)	(2.90%)
Foreign tax credit/transition tax - federal only	2.30%	2.40%
GILTI, net of foreign tax credits	1.10%	2.10%
Change in valuation allowance	1.40%	0.00%
Other	2.40%	0.70%
Provision for income taxes	24.90%	23.70%