Fair Value Measurement and Fair Value of Financial Instruments (Details 4) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Loans:
Impaired loans	$ 1,010		$ 1,022
Loss Impaired loans	(16)	$ (127)
Computer Software, Impairments	(3)
Impairment of Premises and Equipment		(4)
Other assets:
Impairment of Loans Held for Sale	(2)	(3)
Gain (Loss) on Energy Investments	2
Loss on OREO		(1)
Loss on Private equity investments		(12)
Impairment of Intangible Assets, Finite-lived		(1)
Loss, Total	(19)	(148)
Fair Value Measurements, Nonrecurring
Loans:
Impaired loans	139	375
Property, Plant, and Equipment, Fair Value Disclosure		0
Other assets:
Loans Held-for-sale, Fair Value Disclosure	15	5
Renewable energy investment	9
OREO		2
Private Equity Investments		10
Finite-lived Intangible Assets, Fair Value Disclosure		0
Total	163	392
Fair Value Measurements, Nonrecurring | Level 3
Loans:
Impaired loans	139	375
Capitalized Computer Software, Gross	0
Property, Plant, and Equipment, Fair Value Disclosure		0
Other assets:
Loans Held-for-sale, Fair Value Disclosure	15	5
Renewable energy investment	9
OREO		2
Private Equity Investments		10
Finite-lived Intangible Assets, Fair Value Disclosure		0
Total	$ 163	$ 392