CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Activities
Net (loss) income attributable to common stockholders	$ (15,503)	$ 1,365
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	12,358	11,876
Provision for doubtful accounts	15,933	4,264
Stock-based compensation	31,750	31,319
Noncash lease cost	10,378	9,751
Deferred income taxes	(7,450)	(1,259)
Other adjustments, net	(287)	(1,159)
Changes in operating assets and liabilities:
Accounts receivable	5,024	(6,260)
Prepaid expenses and other assets	(4,118)	(5,292)
Operating lease liabilities	(6,663)	(9,948)
Accounts payable, accrued liabilities and other liabilities	(636)	6,372
Net cash provided by operating activities	40,786	41,029
Investing Activities
Sales and maturities of marketable securities — available-for-sale	164,215	0
Purchases of marketable securities — held-to-maturity	(87,438)	(157,567)
Maturities of marketable securities — held-to-maturity	93,200	201,497
Purchases of property, equipment and software	(7,053)	(8,991)
Other investing activities	295	215
Net cash provided by investing activities	163,219	35,154
Financing Activities
Proceeds from issuance of common stock for employee stock-based plans	2,585	1,145
Repurchases of common stock	0	(102,126)
Taxes paid related to the net share settlement of equity awards	(11,514)	(12,497)
Net cash used in financing activities	(8,929)	(113,478)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(486)	(65)
Change in cash, cash equivalents and restricted cash	194,590	(37,360)
Cash, cash equivalents and restricted cash — Beginning of period	192,318	354,835
Cash, cash equivalents and restricted cash — End of period	386,908	317,475
Supplemental Disclosures of Other Cash Flow Information
Refunds received for income taxes, net	(290)	(408)
Supplemental Disclosures of Noncash Investing and Financing Activities
Purchases of property, equipment and software recorded in accounts payable and accrued liabilities	3,015	1,835
Tax liability related to net share settlement of equity awards included in accrued liabilities	1,043	1,172
Repurchases of common stock recorded in accrued liabilities	0	8,510
Operating lease right-of-use assets obtained in exchange for new operating lease liabilities	$ 11,833	$ 6,325