Investments - Summary of Sources of Collateral Received and Various Investment Agreement in which Collateral Pledged (Detail) (Successor [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Cash and Securities Pledged Directly from Investment Portfolio [Member]
Investment [Line Items]
Fair Value of Cash and Underlying Securities	$ 379,423	$ 500,986
Fair Value of Cash and Securities Pledged to Investment and Repurchase Agreement Counterparties	156,916	371,723
Fair Value of Cash and Securities Pledged to Derivative Counterparties	222,507	129,263
Cash and Securities Pledged from Its Derivative Counterparties [Member]
Investment [Line Items]
Fair Value of Cash and Underlying Securities		$ 690