CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	[3]
OPERATING ACTIVITIES:
Net loss attributable to common stockholders	$ (2,286)	$ (4,026)	[1],[2]
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	10,028	10,151	[1]
Provision for doubtful accounts and sales returns	8,143	5,901
Stock-based compensation	27,734	24,334
Other adjustments	(913)	253
Changes in operating assets and liabilities:
Accounts receivable	(6,995)	(4,458)
Prepaid expenses and other assets	(5,074)	(1,653)
Accounts payable, accrued expenses and other liabilities	7,652	10,459
Deferred revenue	7	274
Net cash provided by operating activities	38,296	41,235
INVESTING ACTIVITIES:
Purchases of marketable securities	(280,893)	(73,971)
Maturities of marketable securities	143,000	68,000
Acquisition of a business, net of cash received	0	(30,833)
Purchases of property, equipment and software	(10,927)	(2,452)
Capitalized website and software development costs	(4,698)	(4,208)
Other investing activities	27	29
Net cash used in investing activities	(153,491)	(43,435)
FINANCING ACTIVITIES:
Proceeds from issuance of common stock for employee stock-based plans	5,682	3,287
Repurchases of common stock	(33,309)	0
Taxes paid related to the net share settlement of equity awards	(12,347)	0
Net cash (used in) provided by financing activities	(39,974)	3,287
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(100)	138
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(155,269)	1,225
CASH, CASH EQUIVALENTS AND RESTRICTED CASH—Beginning of period	566,404	289,518
CASH, CASH EQUIVALENTS AND RESTRICTED CASH—End of period	411,135	290,743
SUPPLEMENTAL DISCLOSURES OF OTHER CASH FLOW INFORMATION:
Cash paid (refund received) for income taxes, net	206	(107)
SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Purchases of property, equipment and software recorded in accounts payable, accrued expenses and other liabilities	2,242	596
Tax liability related to net share settlement of equity awards included in accrued liabilities	1,092	0
Repurchases of common stock recorded in accrued liabilities	$ 3,684	$ 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. 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 period presented. See Note 1 below for additional discussion.

[3] 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. See Note 1 below for additional discussion.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.