Other Assets (Detail) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Other Assets [Abstract]
Other assets	[1]	$ 113,896	$ 156,278
Loan servicing assets, at fair value (1)
Other Assets [Abstract]
Other assets		60,160	33,676
Prepaid expenses
Other Assets [Abstract]
Other assets		22,048	23,427
Accounts receivable
Other Assets [Abstract]
Other assets		14,820	10,005
Other investments
Other Assets [Abstract]
Other assets		8,735	10,268
Deferred financing costs
Other Assets [Abstract]
Other assets		2,625	2,952
Receivable from investors
Other Assets [Abstract]
Other assets		2,054	2,318
Servicer reserve receivable
Other Assets [Abstract]
Other assets		968	13,685
Insurance reimbursements receivable
Other Assets [Abstract]
Other assets		0	52,119
Other
Other Assets [Abstract]
Other assets		2,486	7,828
Loan Servicing Rights
Other Assets [Abstract]
Principal balance of underlying loan servicing rights		$ 10,500,000	$ 8,200,000

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