Other Assets (Detail) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Other Assets [Abstract]
Other assets (1)	[1]	$ 156,278	$ 69,644
Insurance reimbursement receivable
Other Assets [Abstract]
Other assets (1)		52,119	0
Loan servicing assets, at fair value
Other Assets [Abstract]
Other assets (1)		33,676	21,398
Prepaid expenses
Other Assets [Abstract]
Other assets (1)		23,427	16,960
Servicer reserve receivable
Other Assets [Abstract]
Other assets (1)		13,685	4,938
Other investments
Other Assets [Abstract]
Other assets (1)		10,268	10,372
Accounts receivable
Other Assets [Abstract]
Other assets (1)		10,005	7,572
Deferred financing costs
Other Assets [Abstract]
Other assets (1)		2,952	1,032
Receivable from investors
Other Assets [Abstract]
Other assets (1)		2,318	1,566
Tenant improvement receivable
Other Assets [Abstract]
Other assets (1)		348	3,290
Other
Other Assets [Abstract]
Other assets (1)		$ 7,480	$ 2,516

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