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	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entities [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$ 14,428,632	$ 14,366,434
Variable Interest Entities [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Loans, Estimated fair value	11,558,331	11,529,384
Long-term debt, Estimated fair value	12,270,124	12,160,544
Loans, Unpaid principal balance	8,413,664	8,168,651
Long-term debt, Unpaid principal balance	$ 9,679,441	$ 9,387,884