Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net income	$ 76,882	$ 53,710
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	12,782	8,993
Amortization of debt issuance costs	15	59
Stock-based compensation expense	26,921	16,306
Cash paid for derivative settlement	(131)
Gain on derivative	(1,010)
Deferred income taxes, net	10,234	2,913
Changes in operating assets and liabilities:
Accounts receivable	(838)	(464)
Prepaid expenses	(3,043)	(1,262)
Inventory	57	434
Deposits and other assets	(153)	(111)
Deferred contract costs	(27,487)	(22,330)
Accounts payable	593	(319)
Income taxes, net	1,445	(2,855)
Accrued commissions and bonuses	(5,144)	(2,767)
Accrued payroll and vacation	1,880	1,088
Deferred revenue	5,565	5,293
Accrued expenses and other current liabilities	1,789	(3,395)
Net cash provided by operating activities	100,357	55,293
Cash flows from investing activities
Net change in funds held for clients	188,914	71,229
Purchases of property and equipment	(31,873)	(21,909)
Net cash provided by investing activities	157,041	49,320
Cash flows from financing activities
Proceeds from issuance of long-term debt		5,440
Repurchases of common stock	(41,689)	(15,187)
Withholding taxes paid related to net share settlement	(18,186)	(14,973)
Principal payments on long-term debt		(562)
Net change in client funds obligation	(188,914)	(71,229)
Payment of debt issuance costs	(56)	(143)
Net cash used in financing activities	(248,845)	(96,654)
Increase in cash and cash equivalents	8,553	7,959
Cash and cash equivalents
Beginning of period	46,077	60,158
End of period	$ 54,630	$ 68,117