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	Dec. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Fair Value of Cash and Underlying Securities	$ 291,545	$ 338,007
Fair Value of Cash and Securities Pledged to Investment and Repurchase Agreement Counterparties	88,940	108,379
Fair Value of Cash and Securities Pledged to Derivative Counterparties	$ 202,605	$ 229,628