Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Contingent liabilities		$ 129,887	$ 0
Accrued compensation (1)		30,549	27,009
Accrued expenses		21,317	19,734
Deferred rent		14,734	11,638
Transaction fee refund reserve		14,528	9,098
Loan trailing fee liability, at fair value		8,432	4,913
Deferred revenue		3,415	2,556
Payable to issuing banks		1,894	1,658
Loan servicing liabilities, at fair value		833	2,846
Credit loss coverage reserve		0	2,529
Reimbursement payable to limited partners of LCAM private funds		0	2,313
Other		2,791	1,325
Total accrued expenses and other liabilities	[1]	228,380	85,619
Accrued cash retention rewards		$ 0	$ 3,000

[1] Includes amounts in consolidated variable interest entities (VIEs) presented separately in the table below.