Fair Value Measurement and Fair Value of Financial Instruments (Details 4) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Loans:
Impaired loans	$ 884		$ 884		$ 1,022
Loss Impaired loans	(5)	$ (16)	(21)	$ (143)
Other assets:
Computer Software, Impairments	0	(1)	(3)	(5)
Impairment of Loans Held for Sale	0	0	(2)	(3)
Gain (Loss) on Energy Investments	0		2
Loss on OREO		0		(1)
Loss on Private equity investments		0		(12)
Impairment of Consolidated Variable Interest Entity Low Income Housing Credit Investments	8		8
Impairment of Intangible Assets, Finite-lived		0		(1)
Loss, Total	(13)	(17)	(32)	(165)
Fair Value Measurements, Nonrecurring
Loans:
Impaired loans	124	180	124	180
Other assets:
Capitalized Computer Software, Gross	0	13	0	13
Loans Held-for-sale, Fair Value Disclosure	7	0	7	0
Renewable energy investment	0		0
OREO		2		2
Private Equity Investments		10		10
Variable Interest Entity, Consolidated, Carrying Amount, Assets	91		91
Finite-lived Intangible Assets, Fair Value Disclosure		0		0
Total	222	205	222	205
Fair Value Measurements, Nonrecurring | Level 3
Loans:
Impaired loans	124	180	124	180
Other assets:
Capitalized Computer Software, Gross	0	13	0	13
Loans Held-for-sale, Fair Value Disclosure	7	0	7	0
Renewable energy investment	0		0
OREO		2		2
Private Equity Investments		10		10
Variable Interest Entity, Consolidated, Carrying Amount, Assets	91		91
Finite-lived Intangible Assets, Fair Value Disclosure		0		0
Total	$ 222	$ 205	$ 222	$ 205