Description of Business and Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) segment	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in financing activities	$ (37,052)	$ (5,224)
Net cash provided by operating activities	$ 75,904	40,431
Number of reportable segments as result of acquisitions | segment	1
Restricted cash, cash equivalents and payroll funds collected	$ 811,500		$ 1,000,000
Accounting Standards Update 2016-09, Statutory Tax Withholding Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in financing activities		(500)
Net cash provided by operating activities		$ 500
Retained Earnings | Accounting Standards Update 2016-09, Forfeiture Rate Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment			$ 300