CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities
Net loss	$ (129,542)	$ (32,079)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	34,013	30,048
Stock-based compensation expense, net of amounts capitalized	116,104	26,363
Amortization of deferred commissions	1,107	688
Recovery of long-term note receivable	0	(1,000)
Amortization of debt discount and issuance costs	726	635
Deferred income taxes	431	3,023
Gain on sale of a private company investment and other	(765)	(6,444)
Changes in assets and liabilities:
Accounts receivable	(1,822)	1,497
Prepaid expenses and other assets	(5,451)	(1,098)
Accounts payable and accrued liabilities	4,596	(2,189)
Accrued interest on financing lease obligation, net of payments	(1,036)	4,894
Accrued compensation	(648)	(730)
Deferred revenue	16,269	7,317
Net cash provided by operating activities	33,982	30,925
Cash flows from investing activities
Purchases of property and equipment	(8,811)	(26,158)
Capitalized internal-use software	(8,857)	(11,771)
Proceeds from sale of a private company investment and other	999	15,453
Net cash used in investing activities	(16,669)	(22,476)
Cash flows from financing activities
Proceeds from initial public offering, net of underwriters' discounts and concurrent private placement	232,509	0
Payments of deferred offering costs	(1,487)	0
Proceeds from stock option exercises	440	128
Employee payroll taxes paid related to net share settlement of restricted stock units	(24,566)	(5,431)
Payments to repurchase common stock	(16)	(144)
Proceeds from term and revolving debt issuance	0	298,500
Repayment of debt	(2,250)	(298,133)
Payment of debt issuance costs and other	0	(1,666)
Proceeds from tenant improvement allowances under lease financing obligation	0	8,281
Net cash provided by financing activities	204,630	1,535
Net increase in cash, cash equivalents and restricted cash	221,943	9,984
Cash, cash equivalents and restricted cash at beginning of period	35,345	23,287
Cash, cash equivalents and restricted cash at end of period	257,288	33,271
Supplemental cash flow data:
Interest paid for term debt	16,445	14,951
Interest paid for financing obligation on leased facility	6,114	0
Income taxes paid	246	357
Non-cash investing and financing transactions:
Stock compensation included in capitalized software costs	1,251	2,510
Accrued unpaid capital expenditures and capitalized software development costs	600	5,862
Accrued unpaid payroll taxes related to net share settlement and offering costs	6,924	0
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	257,120	33,271
Restricted cash (included in other assets)	$ 168	$ 0
Restricted Cash, Noncurrent, Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Cash, cash equivalents and restricted cash at end of period	$ 257,288	$ 33,271