Carrying Value and Fair Value of Blackstone Issued Notes (Parenthetical) (Detail) - Senior Secured Notes	3 Months Ended
	Mar. 31, 2018
5.875% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	5.875%
Debt instrument, maturity date	Mar. 15, 2021
4.750% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	4.75%
Debt instrument, maturity date	Feb. 15, 2023
6.250% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	6.25%
Debt instrument, maturity date	Aug. 15, 2042
5.000% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	5.00%
Debt instrument, maturity date	Jun. 15, 2044
4.450% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	4.45%
Debt instrument, maturity date	Jul. 15, 2045
2.000% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	2.00%
Debt instrument, maturity date	May 19, 2025
1.000% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	1.00%
Debt instrument, maturity date	Oct. 05, 2026
3.150% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	3.15%
Debt instrument, maturity date	Oct. 02, 2027
4.000% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	4.00%
Debt instrument, maturity date	Oct. 02, 2047