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	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entities [Line Items]
Loans, Unpaid principal balance	$ 20,184	$ 4,873
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	14,366,434	13,235,425
Variable Interest Entities [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Loans, Estimated fair value	11,529,384	10,658,963
Long-term Debt, Fair Value	12,160,544	11,155,936
Loans, Unpaid principal balance	8,168,651	7,641,756
Long-term debt, Unpaid principal balance	$ 9,387,884	$ 8,854,530