Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net income (loss)	$ (15,002)	$ (22,526)	$ (30,236)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	7,176	6,293	4,395
Stock-based compensation.	11,101	8,413	5,562
Change in assets and liabilities:
Prepaid expenses	(4,225)	2,244	(3,963)
Accrued revenue	(2,709)	(5,021)	(2,685)
Other current assets	5,070	(8,778)	721
Other long-term assets	223	(5,964)	(36)
Accounts payable	(252)	638	152
Accrued expenses	5,115	6,581	3,890
Deferred lease liability	749	8,768	(21)
Origination of loans held for sale	(11,008)	0	0
Proceeds from sale of loans held for sale	9,117	0	0
Net cash provided by (used in) operating activities	5,355	(9,352)	(22,221)
Investing activities
Sales and maturities of short-term investments	2,741	1,744	1,590
Purchases of short-term investments	(992)	(1,744)	(1,550)
Purchases of property and equipment	(12,113)	(13,567)	(4,607)
Net cash used in investing activities	(10,364)	(13,567)	(4,567)
Financing activities
Issuance costs of redeemable convertible preferred stock	0	0	(9)
Proceeds from tender offer	0	0	2,659
In-substance dividend paid in relation to tender offer	0	0	(2,659)
Proceeds from exercise of stock options	3,003	1,495	1,732
Payment of initial public offering costs	(3,558)	(150)	0
Proceeds from initial public offering, net of underwriting discounts	148,088	0	0
Borrowings from warehouse credit facilities	10,746	0	0
Repayments of warehouse credit facilities	(8,730)	0	0
Other payables - customer escrow deposits related to title services	273	399	1,822
Net cash provided by financing activities	149,822	1,744	3,545
Net change in cash, cash equivalents, and restricted cash	144,813	(21,175)	(23,243)
Cash, cash equivalents, and restricted cash:
Beginning of period	67,845	89,020	112,263
End of period	212,658	67,845	89,020
Supplemental disclosure of non-cash investing and financing activities
Conversion of redeemable convertible preferred stock to common stock	831,331	0	0
Accretion of redeemable convertible preferred stock	(175,915)	(55,502)	(102,224)
Stock-based compensation capitalized in property and equipment	(268)	(100)	(49)
Deferred initial public offering cost accruals	0	(570)	0
Property and equipment additions in accounts payable and accrued expenses	(31)	(3,466)	0
Leasehold improvements paid directly by lessor	$ (822)	$ (520)	$ 0