Segment Reporting - Reportable Segments Financial Data (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Fund level fee revenues
Fund management fees	$ 238.8	$ 272.5	$ 485.1	$ 562.0
Performance fees
Realized	357.7	389.9	440.9	521.7
Unrealized	185.9	(179.0)	784.3	(165.6)
Total performance fees	543.6	210.9	1,225.2	356.1
Investment income (loss)
Realized	26.7	38.9	26.5	51.5
Unrealized	32.3	26.4	78.8	4.2
Total investment income	59.0	65.3	105.3	55.7
Other income	3.2	2.0	5.6	3.2
Total revenues	908.4	608.0	2,028.5	1,091.1
Performance fee related
Realized	166.7	172.4	212.5	234.0
Unrealized	90.4	(75.9)	361.7	(68.0)
Total compensation and benefits	496.1	355.4	1,032.0	666.6
General, administrative, and other indirect expenses	95.8	91.4	189.6	173.7
Interest expense	16.5	15.4	31.5	30.7
Total expenses	705.4	546.9	1,514.9	1,006.3
Net Performance Fees	286.5	114.4	651.0	190.1
Segment assets	10,856.4		10,856.4		$ 9,973.0
Corporate Private Equity
Performance fees
Total performance fees	419.8	69.1	987.8	96.6
Real Assets
Performance fees
Total performance fees	81.7	115.5	139.5	217.7
Global Market Strategies
Performance fees
Total performance fees	13.6	7.4	33.6	9.0
Investment Solutions
Performance fees
Total performance fees	28.5	18.9	64.3	32.8
Operating Segments
Fund level fee revenues
Fund management fees	257.2	279.7	512.8	559.6
Portfolio advisory fees, net	4.9	5.8	8.9	9.0
Transaction fees, net	1.2	2.6	8.9	22.9
Total fund level fee revenues	263.3	288.1	530.6	591.5
Performance fees
Realized	352.7	406.3	435.7	538.3
Unrealized	206.6	(196.0)	838.3	(180.0)
Total performance fees	559.3	210.3	1,274.0	358.3
Investment income (loss)
Realized	10.6	9.3	5.2	16.8
Unrealized	20.6	19.6	36.6	5.7
Total investment income	31.2	28.9	41.8	22.5
Interest income	2.4	2.5	5.8	5.5
Other income	2.8	2.7	8.0	5.8
Total revenues	859.0	532.5	1,860.2	983.6
Compensation and benefits
Direct base compensation	103.4	108.5	211.7	230.3
Indirect base compensation	49.6	38.4	88.6	78.2
Equity-based compensation	36.7	30.9	66.8	62.3
Performance fee related
Realized	170.6	173.0	218.3	234.9
Unrealized	89.3	(78.1)	362.2	(67.3)
Total compensation and benefits	449.6	272.7	947.6	538.4
General, administrative, and other indirect expenses	85.4	78.7	166.0	153.1
Depreciation and amortization expense	7.5	7.3	15.0	14.6
Interest expense	16.4	15.5	31.4	30.7
Total expenses	558.9	374.2	1,160.0	736.8
Economic Net Income	300.1	158.3	700.2	246.8
Net Performance Fees	299.4	115.4	693.5	190.7
Investment Income (Loss)	31.2	28.9	41.8	22.5
Equity-based compensation	36.7	30.9	66.8	62.3
Fee Related Earnings	6.2	44.9	31.7	95.9
Realized Net Performance Fees	182.1	233.3	217.4	303.4
Realized Investment Income (Loss)	10.6	9.3	5.2	16.8
Distributable Earnings	198.9	287.5	254.3	416.1
Segment assets	6,672.6		6,672.6
Operating Segments | Corporate Private Equity
Fund level fee revenues
Fund management fees	117.7	126.8	233.4	254.0
Portfolio advisory fees, net	4.5	5.2	8.3	8.3
Transaction fees, net	1.2	2.6	8.9	22.9
Total fund level fee revenues	123.4	134.6	250.6	285.2
Performance fees
Realized	272.1	337.9	323.4	464.1
Unrealized	142.9	(278.9)	658.2	(372.0)
Total performance fees	415.0	59.0	981.6	92.1
Investment income (loss)
Realized	8.9	18.0	9.1	22.5
Unrealized	13.3	3.0	18.8	(3.1)
Total investment income	22.2	21.0	27.9	19.4
Interest income	0.8	0.9	1.9	1.8
Other income	1.3	1.2	2.6	2.7
Total revenues	562.7	216.7	1,264.6	401.2
Compensation and benefits
Direct base compensation	54.7	53.3	110.1	113.1
Indirect base compensation	18.0	18.2	36.7	37.8
Equity-based compensation	17.8	18.4	32.8	36.2
Performance fee related
Realized	121.6	143.3	147.7	201.9
Unrealized	69.4	(117.4)	297.2	(162.1)
Total compensation and benefits	281.5	115.8	624.5	226.9
General, administrative, and other indirect expenses	28.4	32.0	63.4	62.9
Depreciation and amortization expense	3.7	3.4	7.4	6.8
Interest expense	7.3	7.3	14.1	14.2
Total expenses	320.9	158.5	709.4	310.8
Economic Net Income	241.8	58.2	555.2	90.4
Net Performance Fees	224.0	33.1	536.7	52.3
Investment Income (Loss)	22.2	21.0	27.9	19.4
Equity-based compensation	17.8	18.4	32.8	36.2
Fee Related Earnings	13.4	22.5	23.4	54.9
Realized Net Performance Fees	150.5	194.6	175.7	262.2
Realized Investment Income (Loss)	8.9	18.0	9.1	22.5
Distributable Earnings	172.8	235.1	208.2	339.6
Segment assets	3,153.5		3,153.5
Operating Segments | Real Assets
Fund level fee revenues
Fund management fees	58.2	66.5	114.2	131.7
Portfolio advisory fees, net	0.1	0.1	0.2	0.1
Transaction fees, net	0.0	0.0	0.0	0.0
Total fund level fee revenues	58.3	66.6	114.4	131.8
Performance fees
Realized	39.7	58.8	53.2	60.6
Unrealized	60.6	66.1	139.3	163.8
Total performance fees	100.3	124.9	192.5	224.4
Investment income (loss)
Realized	0.3	(9.5)	(7.8)	(7.3)
Unrealized	6.8	6.7	12.0	2.0
Total investment income	7.1	(2.8)	4.2	(5.3)
Interest income	0.4	0.4	1.0	0.9
Other income	0.3	0.2	0.7	0.6
Total revenues	166.4	189.3	312.8	352.4
Compensation and benefits
Direct base compensation	17.4	18.0	37.1	38.2
Indirect base compensation	19.9	10.1	30.8	19.3
Equity-based compensation	9.3	7.0	18.1	13.2
Performance fee related
Realized	17.4	25.3	24.2	26.1
Unrealized	19.2	26.1	38.5	70.9
Total compensation and benefits	83.2	86.5	148.7	167.7
General, administrative, and other indirect expenses	26.5	18.6	42.1	33.5
Depreciation and amortization expense	1.6	1.5	3.4	3.0
Interest expense	4.4	4.0	8.5	8.0
Total expenses	115.7	110.6	202.7	212.2
Economic Net Income	50.7	78.7	110.1	140.2
Net Performance Fees	63.7	73.5	129.8	127.4
Investment Income (Loss)	7.1	(2.8)	4.2	(5.3)
Equity-based compensation	9.3	7.0	18.1	13.2
Fee Related Earnings	(10.8)	15.0	(5.8)	31.3
Realized Net Performance Fees	22.3	33.5	29.0	34.5
Realized Investment Income (Loss)	0.3	(9.5)	(7.8)	(7.3)
Distributable Earnings	11.8	39.0	15.4	58.5
Segment assets	1,697.8		1,697.8
Operating Segments | Global Market Strategies
Fund level fee revenues
Fund management fees	45.1	52.2	93.2	103.3
Portfolio advisory fees, net	0.3	0.5	0.4	0.6
Transaction fees, net	0.0	0.0	0.0	0.0
Total fund level fee revenues	45.4	52.7	93.6	103.9
Performance fees
Realized	17.2	5.4	22.8	7.2
Unrealized	(1.6)	1.8	12.9	1.5
Total performance fees	15.6	7.2	35.7	8.7
Investment income (loss)
Realized	1.5	0.8	3.9	1.6
Unrealized	0.1	9.9	4.3	7.8
Total investment income	1.6	10.7	8.2	9.4
Interest income	1.0	1.1	2.6	2.6
Other income	1.1	1.2	4.5	2.3
Total revenues	64.7	72.9	144.6	126.9
Compensation and benefits
Direct base compensation	15.2	22.2	32.3	45.4
Indirect base compensation	7.6	7.0	14.2	15.2
Equity-based compensation	7.5	4.4	11.8	9.4
Performance fee related
Realized	8.2	0.7	10.9	1.5
Unrealized	(0.7)	2.0	6.1	0.9
Total compensation and benefits	37.8	36.3	75.3	72.4
General, administrative, and other indirect expenses	21.8	20.2	45.0	39.4
Depreciation and amortization expense	1.3	1.6	2.5	3.1
Interest expense	3.2	2.8	5.8	5.5
Total expenses	64.1	60.9	128.6	120.4
Economic Net Income	0.6	12.0	16.0	6.5
Net Performance Fees	8.1	4.5	18.7	6.3
Investment Income (Loss)	1.6	10.7	8.2	9.4
Equity-based compensation	7.5	4.4	11.8	9.4
Fee Related Earnings	(1.6)	1.2	0.9	0.2
Realized Net Performance Fees	9.0	4.7	11.9	5.7
Realized Investment Income (Loss)	1.5	0.8	3.9	1.6
Distributable Earnings	8.9	6.7	16.7	7.5
Segment assets	892.8		892.8
Operating Segments | Investment Solutions
Fund level fee revenues
Fund management fees	36.2	34.2	72.0	70.6
Portfolio advisory fees, net	0.0	0.0	0.0	0.0
Transaction fees, net	0.0	0.0	0.0	0.0
Total fund level fee revenues	36.2	34.2	72.0	70.6
Performance fees
Realized	23.7	4.2	36.3	6.4
Unrealized	4.7	15.0	27.9	26.7
Total performance fees	28.4	19.2	64.2	33.1
Investment income (loss)
Realized	(0.1)	0.0	0.0	0.0
Unrealized	0.4	0.0	1.5	(1.0)
Total investment income	0.3	0.0	1.5	(1.0)
Interest income	0.2	0.1	0.3	0.2
Other income	0.1	0.1	0.2	0.2
Total revenues	65.2	53.6	138.2	103.1
Compensation and benefits
Direct base compensation	16.1	15.0	32.2	33.6
Indirect base compensation	4.1	3.1	6.9	5.9
Equity-based compensation	2.1	1.1	4.1	3.5
Performance fee related
Realized	23.4	3.7	35.5	5.4
Unrealized	1.4	11.2	20.4	23.0
Total compensation and benefits	47.1	34.1	99.1	71.4
General, administrative, and other indirect expenses	8.7	7.9	15.5	17.3
Depreciation and amortization expense	0.9	0.8	1.7	1.7
Interest expense	1.5	1.4	3.0	3.0
Total expenses	58.2	44.2	119.3	93.4
Economic Net Income	7.0	9.4	18.9	9.7
Net Performance Fees	3.6	4.3	8.3	4.7
Investment Income (Loss)	0.3	0.0	1.5	(1.0)
Equity-based compensation	2.1	1.1	4.1	3.5
Fee Related Earnings	5.2	6.2	13.2	9.5
Realized Net Performance Fees	0.3	0.5	0.8	1.0
Realized Investment Income (Loss)	(0.1)	0.0	0.0	0.0
Distributable Earnings	5.4	$ 6.7	14.0	$ 10.5
Segment assets	$ 928.5		$ 928.5