Income Taxes - Summary of Provision for Income Taxes and U.S. Federal Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018		Sep. 30, 2019	Sep. 30, 2018	[1]
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount [Abstract]
Computed “expected” tax expense	$ 61,479	$ 49,889
Foreign income tax differential	(2,904)	2,359
Excess tax benefit related to stock-based compensation	(10,059)	(7,562)
State taxes net of federal benefits	3,324	3,119
Foreign-sourced nontaxable income	(1)	(5,620)
Foreign withholding	5,150	4,578
GILTI, net of foreign tax credits	2,486	5,576
Tax reform - federal rate reduction	0	22,731
Other	7,477	4,804
Provision for income taxes	$ 66,952	$ 79,874	[1]	$ 119,695	$ 188,579
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Computed “expected” tax expense	21.00%	21.00%
Foreign income tax differential	(1.00%)	1.00%
Excess tax benefit related to stock-based compensation	(3.40%)	(3.20%)
State taxes net of federal benefits	1.10%	1.30%
Foreign-sourced nontaxable income	0.00%	(2.40%)
Foreign withholding	1.80%	1.90%
GILTI, net of foreign tax credits	0.90%	2.40%
Tax reform - federal rate reduction		0.096
Other	2.60%	2.00%
Provision for income taxes	22.90%	33.60%

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