CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	[1]
OPERATING ACTIVITIES:
Net income attributable to common stockholders	$ 23,404	$ 11,874	[2]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	31,250	31,470	[2]
Bad debt expense	19,285	15,239
Stock-based compensation	85,732	75,007
Other adjustments	(2,793)	280
Changes in operating assets and liabilities:
Accounts receivable	(24,956)	(19,810)
Prepaid expenses and other assets	(2,085)	(2,077)
Accounts payable, accrued expenses and other liabilities	(13,647)	15,628
Deferred revenue	(75)	350
Net cash provided by operating activities	116,115	127,961
INVESTING ACTIVITIES:
Purchases of marketable securities	(572,788)	(179,557)
Maturities of marketable securities	460,800	191,000
Acquisition of a business, net of cash received	0	(50,544)
Purchases of property, equipment and software	(18,699)	(7,892)
Capitalized website and software development costs	(15,238)	(12,236)
Other investing activities	64	69
Net cash used in investing activities	(145,861)	(59,160)
FINANCING ACTIVITIES:
Proceeds from issuance of common stock for employee stock-based plans	21,835	29,556
Repurchases of common stock	(71,993)	(7,743)
Taxes paid related to the net share settlement of equity awards	(41,081)	0
Net cash (used in) provided by financing activities	(91,239)	21,813
Effect of exchange rate changes on cash, cash equivalents and restricted cash	197	864
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(120,788)	91,478
CASH, CASH EQUIVALENTS AND RESTRICTED CASH—Beginning of period	566,404	289,518
CASH, CASH EQUIVALENTS AND RESTRICTED CASH—End of period	445,616	380,996
SUPPLEMENTAL DISCLOSURES OF OTHER CASH FLOW INFORMATION:
Cash paid for income taxes, net	28,820	82
SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Purchases of property, equipment and software recorded in accounts payable, accrued expenses and other liabilities	2,393	3,555
Tax liability related to net share settlement of equity awards included in accrued liabilities	$ 1,679	$ 0

[1] As of January 1, 2018, the Company adopted ASC 606 using the full retrospective method. Accordingly, the Company has recast certain amounts in the prior period presented. Also as of January 1, 2018, the Company adopted Accounting Standards Update No. 2016-18, "Statement of Cash Flows (Subtopic 230): Restricted Cash," and recast the prior period presented. See Note 1 below for additional discussion.

[2] As of January 1, 2018, the Company adopted ASC 606 using the full retrospective method. Accordingly, the Company has recast certain amounts in the prior periods presented. See Note 1 below for additional discussion.