Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operating activities
Net loss	$ 3,207	$ 4,304	$ (33,232)	$ (23,762)	$ (15,002)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization			3,902	3,539
Stock-based compensation			8,974	5,320
Change in assets and liabilities:
Prepaid expenses			5,277	1,842
Accrued revenue			(5,568)	(3,885)
Inventories			(11,137)	(1,582)
Other current assets			(1,470)	8,064
Other long-term assets			(125)	377
Accounts payable			1,934	901
Accrued liabilities			7,481	8,481
Deferred lease liability			(583)	1,097
Origination of loans held for sale			(29,249)	(3,022)
Proceeds from sale of loans originated as held for sale			27,555	2,477
Net cash used in operating activities			(26,241)	(153)
Investing activities
Maturities and sales of short-term investments			0	1,239
Purchases of short-term investments			0	(992)
Purchases of property and equipment			(4,045)	(9,435)
Net cash used in investing activities			(4,045)	(9,188)
Financing activities
Proceeds from issuance of common stock			14,394	1,017
Tax payment related to net share settlements on restricted stock units			(227)	0
Payment of initial public offering costs			0	(1,807)
Borrowings from warehouse credit facilities			28,551	2,932
Repayments of warehouse credit facilities			(27,076)	(2,403)
Other payables - customer escrow deposits related to title services			13,631	7,814
Net cash provided by financing activities			29,273	7,553
Net change in cash, cash equivalents, and restricted cash			(1,013)	(1,788)
Cash, cash equivalents, and restricted cash:
Beginning of period			212,658	67,845	67,845
End of period	211,645	66,057	211,645	66,057	$ 212,658
Supplemental disclosure of non-cash investing and financing activities
Accretion of redeemable convertible preferred stock	$ 0	$ (110,921)	0	(135,690)
Stock-based compensation capitalized in property and equipment			(244)	(131)
Initial public offering cost accruals			0	(343)
Property and equipment additions in accounts payable and accrued expenses			(21)	0
Leasehold improvements paid directly by lessor			(926)	(104)
Cash in transit for exercised stock options			$ (30)	$ 0