Investments - Summary of Sources of Collateral Received and Various Investment Agreement in which Collateral Pledged (Detail) (Successor [Member], Cash and Securities Pledged Directly from Investment Portfolio [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Successor [Member] | Cash and Securities Pledged Directly from Investment Portfolio [Member]
Investment [Line Items]
Fair Value of Cash and Underlying Securities	$ 368,979	$ 379,423
Fair Value of Cash and Securities Pledged to Investment and Repurchase Agreement Counterparties	108,469	156,916
Fair Value of Cash and Securities Pledged to Derivative Counterparties	$ 260,510	$ 222,507