Net Investment Income (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Net Investment Income [Line Items]
Interest income		$ 119,200	$ 102,000
Dividend income		9,800	16,400
Investment expenses		(7,500)	(12,000)
Other investment results		300	4,000
Net investment income		123,049	124,126
Limited partnership interests in certain subsidiaries of Ares
Net Investment Income [Line Items]
Equity results	[1]	0	13,700
Pillar Capital Holdings Limited And Managed Funds
Net Investment Income [Line Items]
Equity results	[1]	$ 1,200	$ 0

[1] See Note 3(h) of this Form 10-Q for discussion of the Pillar Investments, as defined therein, and limited partnership interests in certain subsidiaries of Ares.