Net Investment Income (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net Investment Income [Line Items]
Interest income		$ 127,200	$ 104,800	$ 246,500	$ 206,800
Dividend income		9,400	22,300	19,200	38,600
Investment expenses		(7,200)	(6,600)	(14,700)	(18,600)
Other investment results		10,000	4,600	10,400	8,500
Net investment income		142,745	126,273	265,794	250,399
Limited partnership interests in certain subsidiaries of Ares
Net Investment Income [Line Items]
Equity results	[1]		(700)		13,200
Pillar Capital Holdings Limited And Managed Funds
Net Investment Income [Line Items]
Equity results	[1]	$ 3,300	$ 1,900	$ 4,400	$ 1,900

[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.