Comprehensive Income - Schedule of Amounts Reclassed Out of Each Component of Accumulated Other Comprehensive Income (Detail) (Successor [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	$ (1,709)	$ (3,249)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(51,029)	(6,104)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized investment gains	(51,002)	(5,900)
Net of tax and noncontrolling interest	(51,002)	(5,900)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(51,002)	(5,900)
Other Postretirement Benefit Plan, Defined Benefit [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(27)	(204)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax and noncontrolling interest	(51,029)	(6,104)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	0	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	0	0
Prior service cost	(166)	(166)
Actuarial gains (losses)	139	(38)
Total before tax	(27)	(204)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ (27)	$ (204)