Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued expenses		$ 31,113	$ 21,317
Accrued compensation		30,153	30,549
Contingent liabilities (1)		19,089	129,887
Transaction fee refund reserve		18,104	14,528
Deferred rent		15,418	14,734
Loan trailing fee liability, at fair value		9,856	8,432
Deferred revenue		7,443	3,415
Payable to issuing banks		1,096	1,894
Loan servicing liabilities, at fair value		156	833
Other		4,201	2,791
Total accrued expenses and other liabilities	[1]	$ 136,629	$ 228,380

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