Investments in Partnerships, Offshore Funds and Variable Interest Entities, Part I (Details)	3 Months Ended	9 Months Ended
	Dec. 31, 2014 USD ($) Entity	Sep. 30, 2015 USD ($) Entity	Sep. 30, 2014 USD ($) Entity
Variable Interest Entity [Line Items]
Investments in affiliated entities | $	$ 94,200,000	$ 87,200,000	$ 93,200,000
Investments in unaffiliated entities | $	13,400,000	13,800,000	14,200,000
Investments in Partnerships by Accounting Method [Abstract]
Fair value | $	23,803,000	14,317,000	24,094,000
Equity Method Investments | $	83,834,000	86,708,000	83,340,000
Total | $	107,637,000	101,025,000	107,434,000
Maximum exposure to loss related to VIEs | $	10,600,000	9,600,000	8,600,000
Deferred carried interest in VIE | $	43,000	38,000	44,000
Total VIE assets | $	$ 71,600,000	$ 65,800,000	$ 59,800,000
VIE [Member]
Entities Consolidated [Roll Forward]
Entities consolidated at beginning of period	1	1	1
Additional consolidated entities	0	1	0
Deconsolidated entities	0	0	0
Entities consolidated at end of period	1	2	1
Investments in Partnerships by Accounting Method [Abstract]
Total | $	$ 13,434,000	$ 5,116,000	$ 13,618,000
VOE [Member]
Entities Consolidated [Roll Forward]
Entities consolidated at beginning of period	4	4	4
Additional consolidated entities	0	2	0
Deconsolidated entities	0	(2)	0
Entities consolidated at end of period	4	4	4
Prior to Consolidations [Member]
Investments in Partnerships by Accounting Method [Abstract]
Total | $	$ 111,380,000	$ 105,097,000	$ 110,679,000
CFFs [Member]
Investments in Partnerships by Accounting Method [Abstract]
Total | $	4,438,000	4,817,000	4,684,000
CFFs [Member] | Affiliated [Member]
Investments in Partnerships by Accounting Method [Abstract]
Fair value | $	23,803,000	14,317,000	24,094,000
Equity Method Investments | $	0	0	0
Total | $	$ 23,803,000	$ 14,317,000	$ 24,094,000
CFFs [Member] | VIE [Member]
Entities Consolidated [Roll Forward]
Entities consolidated at beginning of period	1	1	1
Additional consolidated entities	0	0	0
Deconsolidated entities	0	0	0
Entities consolidated at end of period	1	1	1
CFFs [Member] | VOE [Member]
Entities Consolidated [Roll Forward]
Entities consolidated at beginning of period	2	2	2
Additional consolidated entities	0	1	0
Deconsolidated entities	0	(1)	0
Entities consolidated at end of period	2	2	2
Partnerships [Member]
Investments in Partnerships by Accounting Method [Abstract]
Total | $	$ (8,181,000)	$ (8,504,000)	$ (7,929,000)
Partnerships [Member] | Affiliated [Member]
Investments in Partnerships by Accounting Method [Abstract]
Fair value | $	0	0	0
Equity Method Investments | $	34,385,000	38,318,000	34,967,000
Total | $	34,385,000	38,318,000	34,967,000
Partnerships [Member] | Unaffiliated [Member]
Investments in Partnerships by Accounting Method [Abstract]
Fair value | $	0	0	0
Equity Method Investments | $	6,552,000	6,286,000	6,611,000
Total | $	$ 6,552,000	$ 6,286,000	$ 6,611,000
Partnerships [Member] | VIE [Member]
Entities Consolidated [Roll Forward]
Entities consolidated at beginning of period	0	0	0
Additional consolidated entities	0	0	0
Deconsolidated entities	0	0	0
Entities consolidated at end of period	0	0	0
Partnerships [Member] | VOE [Member]
Entities Consolidated [Roll Forward]
Entities consolidated at beginning of period	1	1	1
Additional consolidated entities	0	1	0
Deconsolidated entities	0	0	0
Entities consolidated at end of period	1	2	1
Offshore Funds [Member]
Investments in Partnerships by Accounting Method [Abstract]
Total | $	$ 0	$ (385,000)	$ 0
Offshore Funds [Member] | Affiliated [Member]
Investments in Partnerships by Accounting Method [Abstract]
Fair value | $	0	0	0
Equity Method Investments | $	36,033,000	34,552,000	34,185,000
Total | $	36,033,000	34,552,000	34,185,000
Offshore Funds [Member] | Unaffiliated [Member]
Investments in Partnerships by Accounting Method [Abstract]
Fair value | $	0	0	0
Equity Method Investments | $	6,864,000	7,552,000	7,577,000
Total | $	$ 6,864,000	$ 7,552,000	$ 7,577,000
Offshore Funds [Member] | VIE [Member]
Entities Consolidated [Roll Forward]
Entities consolidated at beginning of period	0	0	0
Additional consolidated entities	0	1	0
Deconsolidated entities	0	0	0
Entities consolidated at end of period	0	1	0
Offshore Funds [Member] | VOE [Member]
Entities Consolidated [Roll Forward]
Entities consolidated at beginning of period	1	1	1
Additional consolidated entities	0	0	0
Deconsolidated entities	0	(1)	0
Entities consolidated at end of period	1	0	1