Net Investment Income (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net Investment Income [Line Items]
Interest income		$ 130,100	$ 106,400	$ 376,600	$ 313,200
Dividend income		9,700	16,200	28,900	54,900
Investment expenses		(7,400)	(6,800)	(22,100)	(25,400)
Other investment results		8,200	5,300	18,600	13,600
Net investment income		147,829	127,329	413,623	377,728
Limited partnership interests in certain subsidiaries of Ares
Net Investment Income [Line Items]
Equity results	[1]		7,000		20,200
Pillar Capital Holdings Limited And Managed Funds
Net Investment Income [Line Items]
Equity results	[1]	$ 7,200	$ (800)	$ 11,600	$ 1,200

[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.