Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid income taxes	$ 47,196	$ 30,314
Prepaid sales and other taxes	10,751	22,973
Prepaid equipment and software maintenance	21,876	26,354
Deferred commissions	41,955	35,044
Other prepaid expenses	22,871	28,866
Other current assets	18,711	29,302
Total	163,360	172,853
Commission and incentive payments
Capitalized Contract Cost [Line Items]
Total deferred costs	68,293	58,580
Commission and incentive payments | Deferred costs included in prepaid and other current assets
Capitalized Contract Cost [Line Items]
Total deferred costs	41,955	35,044
Commission and incentive payments | Deferred costs included in other assets
Capitalized Contract Cost [Line Items]
Total deferred costs	26,338	23,536
Deferred commissions
Capitalized Contract Cost [Line Items]
Amortization expense	$ 45,000	$ 37,600	$ 35,000