Investments - Summary of Sources of Collateral Received and Various Investment Agreement in which Collateral Pledged (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Fair Value of Securities Placed in Trust	$ 381,249	$ 396,100
Successor [Member] | Cash and Securities Pledged Directly from Investment Portfolio [Member]
Investment [Line Items]
Fair Value of Cash and Underlying Securities	368,086	338,007
Fair Value of Cash and Securities Pledged to Investment and Repurchase Agreement Counterparties	108,367	108,379
Fair Value of Cash and Securities Pledged to Derivative Counterparties	$ 259,719	$ 229,628