CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating Activities
Net (loss) income attributable to common stockholders	$ (39,493)	$ 13,668
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	24,940	24,116
Provision for doubtful accounts	21,897	8,716
Stock-based compensation	62,335	61,770
Noncash lease cost	20,984	21,433
Deferred income taxes	(14,263)	(1,912)
Other adjustments, net	876	(1,632)
Changes in operating assets and liabilities:
Accounts receivable	12,910	(17,143)
Prepaid expenses and other assets	604	(5,335)
Operating lease liabilities	(22,520)	(20,299)
Accounts payable, accrued liabilities and other liabilities	(11,021)	14,464
Net cash provided by operating activities	57,249	97,846
Investing Activities
Sales and maturities of marketable securities — available-for-sale	290,395	0
Purchases of marketable securities — held-to-maturity	(87,438)	(289,100)
Maturities of marketable securities — held-to-maturity	93,200	397,197
Release of escrow deposit	0	28,750
Purchases of property, equipment and software	(17,004)	(19,214)
Other investing activities	328	276
Net cash provided by investing activities	279,481	117,909
Financing Activities
Proceeds from issuance of common stock for employee stock-based plans	10,808	11,198
Repurchases of common stock	0	(397,613)
Taxes paid related to the net share settlement of equity awards	(12,557)	(22,605)
Other financing activities	(356)	0
Net cash used in financing activities	(2,105)	(409,020)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(340)	(24)
Change in cash, cash equivalents and restricted cash	334,285	(193,289)
Cash, cash equivalents and restricted cash — Beginning of period	192,318	354,835
Cash, cash equivalents and restricted cash — End of period	526,603	161,546
Supplemental Disclosures of Other Cash Flow Information
(Refund received) cash paid for income taxes, net	(298)	2,843
Supplemental Disclosures of Noncash Investing and Financing Activities
Purchases of property, equipment and software recorded in accounts payable and accrued liabilities	615	2,271
Tax liability related to net share settlement of equity awards included in accrued liabilities	0	982
Repurchases of common stock recorded in accrued liabilities	0	2,381
Operating lease right-of-use assets obtained in exchange for new operating lease liabilities	$ 11,833	$ 6,325