Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities
Net income (loss)	$ (2,231)	$ (18,708)	$ (24,356)
Adjustments to reconcile net loss to net cash provided by operating activities:
Provision for loan losses	74,863	67,432	26,570
Depreciation and amortization	6,508	4,071	2,645
Amortization of debt issuance costs	2,837	2,676	2,184
Stock-based compensation	11,582	2,842	438
Loss on disposal	0	516	0
Debt discount	0	0	959
Preferred stock warrant issuance and warrant liability fair value adjustment	0	11,232	3,739
Amortization of net deferred origination costs	32,939	27,267	17,322
Changes in servicing rights, at fair value	1,270	0	0
Gain on sales of loans	(53,354)	(8,823)	(788)
Unfunded loan commitment reserve	2,922	1,253	0
Common stock warrant issuance	0	64	45
Gain on extinguishment of debt	(421)	0	0
Changes in operating assets and liabilities:
Other assets	(12,269)	(2,681)	(143)
Accounts payable	236	1,599	(570)
Interest payable	(62)	(301)	(53)
Accrued expenses and other liabilities	16,034	6,034	4,028
Originations of loans held for sale	(445,968)	(140,578)	(18,835)
Payments of net deferred origination costs of loans held for sale	(17,601)	(6,116)	(1,310)
Proceeds from sale of loans held for sale	489,364	154,070	19,510
Principal repayments of loans held for sale	12,298	1,347	0
Net cash provided by operating activities	118,947	103,196	31,385
Cash flows from investing activities
Change in restricted cash	(9,015)	(14,606)	(5,647)
Purchases of property, equipment and software	(13,692)	(7,576)	(3,705)
Capitalized internal-use software	(4,197)	(3,467)	(2,093)
Originations of term loans and lines of credit, excluding rollovers into new originations	(1,162,537)	(858,297)	(380,357)
Proceeds from sale of loans held for investment	177,014	0	0
Payments of net deferred origination costs	(28,353)	(34,253)	(23,180)
Principal repayments of term loans and lines of credit	872,551	546,629	238,253
Other	(186)	0	0
Net cash used in investing activities	(168,415)	(371,570)	(176,729)
Cash flows from financing activities
Investments by noncontrolling interests	7,873	0	0
Proceeds from exercise of stock options and warrants	251	4,625	389
Proceeds from public offering, net of underwriting discount	0	213,843	0
Payments of initial public offering costs	(1,845)	(2,239)	0
Redemption of common stock and warrants	(187)	0	(6,123)
Issuance of common stock under employee stock purchase plan	1,825	0	0
Proceeds from the issuance of redeemable convertible preferred stock	0	77,000	49,717
Redemption of preferred stock	0	0	(6,282)
Payments of debt issuance costs	(1,690)	(5,723)	(2,071)
Net cash provided by financing activities	(10,468)	484,137	142,628
Effect of exchange rate changes on cash and cash equivalents	(675)	0	0
Net increase (decrease) in cash and cash equivalents	(60,611)	215,763	(2,716)
Cash and cash equivalents at beginning of year	220,433	4,670	7,386
Cash and cash equivalents at end of year	159,822	220,433	4,670
Supplemental disclosure of other cash flow information
Cash paid for interest	15,394	14,968	10,616
Supplemental disclosures of non-cash investing and financing activities
Loans transferred from loans held for sale to loans held for investment	1,348	0	0
Conversion of redeemable convertible preferred stock to common stock	0	221,504	0
Unpaid offering expenses charged to equity	0	1,670	0
Stock-based compensation included in capitalized internal-use software	877	253	10
Unpaid principal balance of term loans rolled into new originations	265,933	158,876	59,623
Conversion of debt to redeemable convertible preferred stock	0	0	8,959
Accretion of dividends on redeemable convertible preferred stock	0	12,884	7,470
Funding debt
Cash flows from financing activities
Proceeds from the issuance of debt	212,562	472,242	201,860
Repayment of debt	(219,957)	(272,611)	(109,862)
Corporate debt
Cash flows from financing activities
Proceeds from the issuance of debt	2,700	9,000	15,000
Repayment of debt	$ (12,000)	$ (12,000)	$ 0