Long-Term Borrowings - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2015
Debt Instrument [Line Items]
Minimum redemption or purchase price required	$ 253.0	$ 253.0
APEX exchanged, par amount	650.0	1,320.0
Series E and Series F Preferred Stock canceled, redemption value	650.0	$ 1,320.0
Subordinated Debt [Member]
Debt Instrument [Line Items]
Subordinated debt maturities, description		As of both September 2016 and December 2015, subordinated debt had maturities ranging from 2017 to 2045.
Subordinated debt maturities, range, start		Dec. 31, 2017	Dec. 31, 2017
Subordinated debt maturities, range, end		Dec. 31, 2045	Dec. 31, 2045
The 2012 Trusts [Member]
Debt Instrument [Line Items]
Junior subordinated debt held by Murray Street	$ 1,750.0	$ 1,750.0
Interest Rate of Junior Subordinated Debt held by Murray Street Trust, Fixed	4.647%	4.647%
Maturity date of Junior Subordinated Debt held by Murray Street Trust		Mar. 09, 2017
Junior subordinated debt held by Vesey Street	$ 500.0	$ 500.0
Interest Rate of Junior Subordinated Debt held by Vesey Street Trust, Fixed	4.404%	4.404%
Maturity date of Junior Subordinated Debt held by Vesey Street Trust		Sep. 01, 2016
Senior guaranteed trust securities issued by the Murray Street Trust and Vesey Street Trust (together, the 2012 Trusts)	$ 2,250.0	$ 2,250.0
Senior guaranteed trust securities held by the firm exchanged with the firm's junior subordinated debt securities held by the Trust				$ 175.0
Firm's Junior subordinated debt securities held by the Trust exchanged with senior guaranteed trust securities held by the firm				175.0
Goldman Sachs Capital I [Member]
Debt Instrument [Line Items]
Interest Rate of Junior Subordinated Debentures issued to Trust, Fixed	6.345%	6.345%
Maturity date of Junior Subordinated Debentures issued to Trust		Feb. 15, 2034
Junior subordinated debentures issued to Goldman Sachs Capital I (Trust)	$ 2,840.0	$ 2,840.0
Guaranteed preferred beneficial interests issued to third parties	2,750.0	2,750.0
Common beneficial interests issued to Group Inc.	85.0	85.0
Common beneficial interests delivered to the Trust				44.2	$ 44.2
Trust Preferred Securities purchased, par amount				$ 1,430.0	$ 1,430.0
Junior subordinated debt, outstanding par amount	1,360.0	1,360.0
Trust Preferred Securities, outstanding par amount	1,320.0	1,320.0
Common beneficial interests, outstanding par amount	$ 40.8	$ 40.8
Interest Rate of Junior Subordinated Debentures held by certain third parties	6.345%	6.345%
Maturity date of Junior Subordinated Debentures held by certain third parties		Feb. 15, 2034