Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Thousands		Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued expenses		$ 36,797		$ 42,507
Accrued compensation		30,484		36,105
Transaction fee refund reserve		25,541		19,543
Contingent liabilities		16,000	$ 16,000	12,750
Deferred revenue		13,688		9,420
Loan trailing fee liability, at fair value		11,099		10,010
Payable to issuing banks		1,332		1,182
Deferred rent				16,211
Other		7,695		4,390
Total accrued expenses and other liabilities	[1]	$ 142,636		$ 152,118

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