Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net income (loss)	$ (85,482)	$ (2,231)	$ (18,708)
Adjustments to reconcile net loss to net cash provided by operating activities:
Provision for loan losses	149,963	74,863	67,432
Depreciation and amortization	9,462	6,508	4,071
Amortization of debt issuance costs	4,538	2,837	2,676
Stock-based compensation	15,915	11,582	2,842
Loss on disposal	0	0	516
Preferred stock warrant issuance and warrant liability fair value adjustment	0	0	11,232
Amortization of net deferred origination costs	36,040	32,939	27,267
Changes in servicing rights, at fair value	4,997	1,270	0
Gain on sales of loans	(14,411)	(53,354)	(8,823)
Unfunded loan commitment reserve	(307)	2,922	1,253
Common stock warrant issuance	0	0	64
Gain on extinguishment of debt	(1,372)	(421)	0
Changes in operating assets and liabilities:
Other assets	(1,942)	(12,269)	(2,681)
Accounts payable	2,570	236	1,599
Interest payable	1,365	(62)	(301)
Accrued expenses and other liabilities	5,580	16,034	6,034
Originations of loans held for sale	(304,258)	(445,968)	(140,578)
Capitalized net deferred origination costs of loans held for sale	(10,269)	(17,601)	(6,116)
Proceeds from sale of loans held for sale	314,627	489,364	154,070
Principal repayments of loans held for sale	7,235	12,298	1,347
Net cash provided by operating activities	134,251	118,947	103,196
Cash flows from investing activities
Change in restricted cash	(5,969)	(9,015)	(14,606)
Purchases of property, equipment and software	(6,640)	(13,692)	(7,576)
Capitalized internal-use software	(4,645)	(4,197)	(3,467)
Originations of term loans and lines of credit, excluding rollovers into new originations	(1,826,085)	(1,162,537)	(858,297)
Proceeds from sale of loans held for investment	75,787	177,014	0
Payments of net deferred origination costs	(47,082)	(28,353)	(34,253)
Principal repayments of term loans and lines of credit	1,232,272	872,551	546,629
Other	(201)	(186)	0
Purchase of loans	(6,671)	0	0
Net cash used in investing activities	(589,234)	(168,415)	(371,570)
Cash flows from financing activities
Investments by noncontrolling interests	0	7,873	0
Purchase of treasury shares	(855)	0	0
Proceeds from exercise of stock options and warrants	197	251	4,625
Proceeds from public offering, net of underwriting discount	0	0	213,843
Payments of initial public offering costs	0	(1,845)	(2,239)
Redemption of common stock and warrants	0	(187)	0
Issuance of common stock under employee stock purchase plan	2,606	1,825	0
Proceeds from the issuance of redeemable convertible preferred stock	0	0	77,000
Payments of debt issuance costs	(6,281)	(1,690)	(5,723)
Net cash provided by (used in) financing activities	374,728	(10,468)	484,137
Effect of exchange rate changes on cash and cash equivalents	(13)	(675)	0
Net increase (decrease) in cash and cash equivalents	(80,268)	(60,611)	215,763
Cash and cash equivalents at beginning of year	159,822	220,433	4,670
Cash and cash equivalents at end of year	79,554	159,822	220,433
Supplemental disclosure of other cash flow information
Cash paid for interest	24,778	15,394	14,968
Supplemental disclosures of non-cash investing and financing activities
Loans transferred from loans held for sale to loans held for investment	884	1,348	0
Conversion of redeemable convertible preferred stock to common stock	0	0	221,504
Unpaid offering expenses charged to equity	0	0	1,670
Stock-based compensation included in capitalized internal-use software	1,470	877	253
Unpaid principal balance of term loans rolled into new originations	273,453	265,933	158,876
Accretion of dividends on redeemable convertible preferred stock	0	0	12,884
Funding debt
Cash flows from financing activities
Proceeds from the issuance of debt	752,443	212,562	472,242
Repayment of debt	(398,682)	(219,957)	(272,611)
Corporate debt
Cash flows from financing activities
Proceeds from the issuance of debt	25,300	2,700	9,000
Repayment of debt	$ 0	$ (12,000)	$ (12,000)