Investments - Investments, at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	$ 1,736,703	$ 1,744,412
Investment Cost	1,588,840	1,649,828
Percentage of Net Assets of Consolidated Investments Funds	100.20%	100.00%
Other Investments [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	1,734	1,588
Investment Cost	3,272	3,563
AAA [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	1,659,093	1,666,448
Investment Cost	1,498,965	1,561,154
Percentage of Net Assets of Consolidated Investments Funds	98.60%	98.50%
Apollo Senior Loan Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	27,218	27,653
Investment Cost	27,131	27,296
Percentage of Net Assets of Consolidated Investments Funds	1.60%	1.50%
HFA [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	48,658	48,723
Investment Cost	59,472	57,815
Private Equity Segment [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	1,660,827	1,668,036
Private Equity Segment [Member] | Other Investments [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	1,734	1,588
Private Equity Segment [Member] | AAA [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	1,659,093	1,666,448
Credit [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	75,876	76,376
Credit [Member] | Apollo Senior Loan Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	27,218	27,653
Credit [Member] | HFA [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments, at Fair Value	$ 48,658	$ 48,723