Reclassifications of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		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)
Other than temporary impairment losses		3,597	3	13,617	514
Income taxes		28,010	60,413	207,878	171,275
Unrealized Appreciation of Investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications		(4,900)	(12,800)	(10,200)	(16,500)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Appreciation of Investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized capital gains	[1]	(9,800)	(16,200)	(26,600)	(21,500)
Other than temporary impairment losses		3,600		13,600	500
Income taxes		$ 1,300	$ 3,400	$ 2,800	$ 4,500

[1] For the three and nine months ended September 30, 2019, excludes a $5.8 million pre-tax loss related to the decrease in the fair value of the Put Option. See Note 3(d) for additional information. For the nine months ended September 30, 2018, excludes a $45.7 million pre-tax gain from AIHL’s conversion of its limited partnership interests in certain subsidiaries of Ares into Ares common units. See Note 3(h) of this Form 10-Q for additional information.