Other Assets - Intangible Assets Disclosure (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 1,573	$ 1,521
Accumulated amortization	(1,138)	(1,030)
Net carrying amount	$ 435	491
Identifiable intangible assets approximate weighted average remaining life in years	5 years
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 1,065	1,072
Accumulated amortization	(820)	(777)
Net carrying amount	$ 245	295
Identifiable intangible assets approximate weighted average remaining life in years	5 years
Commodities-Related Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 184	185
Accumulated amortization	(119)	(94)
Net carrying amount	$ 65	91
Identifiable intangible assets approximate weighted average remaining life in years	7 years
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 324	264
Accumulated amortization	(199)	(159)
Net carrying amount	$ 125	$ 105
Identifiable intangible assets approximate weighted average remaining life in years	5 years