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) (Variable Interest Entities [Member], Successor Ambac [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Variable Interest Entities [Member] | Successor Ambac [Member]
Variable Interest Entities [Line Items]
Loans, Estimated fair value	$ 13,269,452	$ 13,398,895
Long-term debt, Estimated fair value	13,878,577	14,091,753
Loans, Unpaid principal balance	11,785,529	12,226,481
Long-term debt, Unpaid principal balance	$ 13,828,951	$ 14,251,771