CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net loss	$ (154,740)	$ (24,010)	$ (76,350)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	47,166	42,391	36,698
Stock-based compensation expense, net of amounts capitalized	131,770	34,986	32,957
Amortization of debt discount and issuance costs	902	876	1,879
Deferred income taxes	(508)	(16,848)	4,420
Loss on debt extinguishment	941	194	0
Gain on sale of a private company investment	(999)	(6,750)	0
Impairment of property and equipment	2,821	0	0
Derecognition of goodwill and intangible assets	0	0	15,895
Other	1,798	(829)	2,870
Changes in assets and liabilities:
Accounts receivable	(1,958)	675	27
Prepaid expenses and other assets	(5,565)	867	(3,508)
Accounts payable and accrued liabilities	3,564	(2,061)	8,682
Accrued interest on financing lease obligation, net of payments	(1,376)	4,580	6,924
Accrued compensation	5,203	2,327	783
Deferred revenue	16,353	8,628	4,565
Net cash provided by operating activities	45,372	45,026	35,842
Cash flows from investing activities
Purchases of property and equipment	(9,981)	(32,488)	(30,419)
Capitalized internal-use software	(12,052)	(15,319)	(15,834)
Proceeds from sale of a private company investment and other	999	15,453	(650)
Net cash used in investing activities	(21,034)	(32,354)	(46,903)
Cash flows from financing activities
Proceeds from initial public offering, net of underwriters' discounts and concurrent private placement	232,509	0	0
Payments of deferred offering costs	(7,173)	0	0
Proceeds from stock option exercises	494	153	201
Employee payroll taxes paid for net share settlement of restricted stock units	(25,807)	(6,934)	(11,934)
Payments to repurchase common stock	(16)	(144)	0
Payment of deferred acquisition purchase consideration	0	0	(15,079)
Proceeds from term and revolving debt issuance	0	298,500	25,000
Repayment of debt	(104,050)	(298,883)	(3,090)
Payment of debt issuance costs and other	(482)	(1,666)	0
Proceeds from tenant improvement allowances under lease financing obligation	0	8,360	5,516
Net cash provided by (used in) financing activities	95,475	(614)	614
Effect of exchange rate changes on cash	(787)	0	0
Net increase (decrease) in cash, cash equivalents and restricted cash	119,026	12,058	(10,447)
Cash, cash equivalents and restricted cash at beginning of period	35,345	23,287	33,734
Cash, cash equivalents and restricted cash at end of period	154,371	35,345	23,287
Supplemental cash flow data:
Interest paid for term debt	20,466	19,864	19,828
Interest paid for financing obligation on leased facility	8,152	2,038	6,908
Income taxes paid	535	547	1,419
Non-cash investing and financing transactions:
Stock compensation included in capitalized software costs	2,609	3,119	5,867
Accrued unpaid capital expenditures	322	1,214	9,343
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	153,807	35,345	23,287
Restricted cash (included in other assets)	$ 564	$ 0	$ 0
Restricted Cash, Noncurrent Asset, Statement of Financial Position Extensible List	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Cash, cash equivalents and restricted cash at end of period	$ 154,371	$ 35,345	$ 23,287