Reclassifications of Accumulated Other Comprehensive Income (Parenthetical) (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Mar. 15, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized capital gains		$ 3,957	$ 16,230	$ 20,753	$ 67,197
Put Option | Equity Contract
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Decrease in fair value of derivative recorded as a reduction to net realized capital gains		5,800		5,800
Insurance Segment | Put Option | Equity Contract
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Decrease in fair value of derivative recorded as a reduction to net realized capital gains		$ 5,800		$ 5,800
Insurance Segment | Ares
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized capital gains	$ 45,700				$ 45,700