Investments - Partnership's Equity Method Investees, Summarized Balance Sheet Information (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Balance sheet information
Investments	$ 86,510.7	$ 68,441.3
Total assets	91,334.4	72,249.8
Debt	5,417.9	2,236.3
Other liabilities	1,441.0	1,389.7
Total liabilities	6,858.9	3,626.0
Partners’ capital	84,475.5	68,623.8
Corporate Private Equity
Balance sheet information
Investments	42,129.8	31,427.7
Total assets	44,987.0	33,605.0
Debt	2,141.8	416.2
Other liabilities	693.2	607.2
Total liabilities	2,835.0	1,023.4
Partners’ capital	42,152.0	32,581.6
Real Assets
Balance sheet information
Investments	24,352.0	21,460.2
Total assets	25,894.9	22,666.0
Debt	2,633.0	1,552.9
Other liabilities	239.6	384.1
Total liabilities	2,872.6	1,937.0
Partners’ capital	23,022.3	20,729.0
Global Credit
Balance sheet information
Investments	3,873.5	2,240.8
Total assets	4,050.0	2,502.5
Debt	508.1	170.4
Other liabilities	128.7	94.3
Total liabilities	636.8	264.7
Partners’ capital	3,413.2	2,237.8
Investment Solutions
Balance sheet information
Investments	16,155.4	13,312.6
Total assets	16,402.5	13,476.3
Debt	135.0	96.8
Other liabilities	379.5	304.1
Total liabilities	514.5	400.9
Partners’ capital	$ 15,888.0	$ 13,075.4