CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating Activities
Net (loss) income attributable to common stockholders	$ (40,513)	$ 23,729
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	37,484	36,507
Provision for doubtful accounts	26,802	15,259
Stock-based compensation	92,590	91,006
Noncash lease cost	31,545	31,379
Deferred income taxes	(6,505)	(673)
Other adjustments, net	1,316	(2,559)
Changes in operating assets and liabilities:
Accounts receivable	(4,783)	(29,395)
Prepaid expenses and other assets	1,552	(2,312)
Operating lease liabilities	(34,284)	(31,002)
Accounts payable, accrued liabilities and other liabilities	23,181	17,329
Net cash provided by operating activities	128,385	149,268
Investing Activities
Sales and maturities of marketable securities — available-for-sale	290,395	0
Purchases of marketable securities — held-to-maturity	(87,438)	(396,648)
Maturities of marketable securities — held-to-maturity	93,200	530,597
Release of escrow deposit	0	28,750
Purchases of property, equipment and software	(24,072)	(29,950)
Other investing activities	329	383
Net cash provided by investing activities	272,414	133,132
Financing Activities
Proceeds from issuance of common stock for employee stock-based plans	11,620	15,813
Repurchases of common stock	0	(474,993)
Taxes paid related to the net share settlement of equity awards	(12,557)	(32,784)
Other financing activities	(433)	0
Net cash used in financing activities	(1,370)	(491,964)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(132)	258
Change in cash, cash equivalents and restricted cash	399,297	(209,306)
Cash, cash equivalents and restricted cash — Beginning of period	192,318	354,835
Cash, cash equivalents and restricted cash — End of period	591,615	145,529
Supplemental Disclosures of Other Cash Flow Information
Cash paid for income taxes, net	109	5,702
Supplemental Disclosures of Noncash Investing and Financing Activities
Purchases of property, equipment and software recorded in accounts payable and accrued liabilities	2,168	1,856
Tax liability related to net share settlement of equity awards included in accounts payable and accrued liabilities	0	896
Operating lease right-of-use assets obtained in exchange for new operating lease liabilities	$ 11,833	$ 6,325