Related Party Transactions and Interests in Consolidated Entities - Due from Affiliates and Due to Affiliates (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Due from Affiliates:
Total Due from Affiliates	$ 209,280	$ 173,312
Due to Affiliates:
Total Due to Affiliates	546,970	477,451
Private Equity Segment [Member]
Due from Affiliates:
Total Due from Affiliates	32,183	28,201
Due to Affiliates:
Total Due to Affiliates	27,738	12,761
Portfolio companies [Member]
Due from Affiliates:
Total Due from Affiliates	17,092	46,048
Credit Segment [Member]
Due from Affiliates:
Total Due from Affiliates	122,745	68,278
Due to Affiliates:
Total Due to Affiliates	561	19,926
Employees [Member]
Due from Affiliates:
Total Due from Affiliates	16,801	9,536
Due to Affiliates:
Total Due to Affiliates	28,809	1,567
Real Estate Segment [Member]
Due from Affiliates:
Total Due from Affiliates	19,367	17,950
Due to Affiliates:
Total Due to Affiliates		1,200
Other Affiliates [Member]
Due from Affiliates:
Total Due from Affiliates	1,092	3,299
Managing Partners [Member]
Due to Affiliates:
Total Due to Affiliates	$ 489,862	$ 441,997