Special Purpose Entities, Including Variable Interest Entities - Supplemental Information about Loans Held as Assets and Long-Term Debt Associated with Consolidated Variable Interest Entities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$ 7,245,870	$ 14,366,434
Variable Interest Entities [Member] \| Successor [Member]
Variable Interest Entities [Line Items]
Loans, Estimated fair value	4,563,091	11,529,384
Long-term debt, Estimated fair value	5,585,860	12,160,544
Loans, Unpaid principal balance	3,654,644	8,168,651
Long-term debt, Unpaid principal balance	$ 4,831,033	$ 9,387,884

Special Purpose Entities, Including Variable Interest Entities - Supplemental Information about Loans Held as Assets and Long-Term Debt Associated with Consolidated Variable Interest Entities (Detail) - USD ($)
$ in Thousands

Sep. 30, 2018

Dec. 31, 2017

Variable Interest Entities [Line Items]

Variable Interest Entity, Consolidated, Carrying Amount, Liabilities

$ 7,245,870

$ 14,366,434

Variable Interest Entities [Member] | Successor [Member]

Variable Interest Entities [Line Items]

Loans, Estimated fair value

4,563,091

11,529,384

Long-term debt, Estimated fair value