Fair Value Disclosures (Assets Measured at Fair Value on a Non-Recurring Basis) (Details) - Nonrecurring - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value
Loans	$ 2,409		$ 2,318
Other assets-Other investments			144
Other assets-Premises, equipment and software costs	0
Total assets	2,409		2,462
Other liabilities and accrued expenses-Lending commitments	213		196
Total liabilities	213		196
Assets
Fair Value
Gains (losses) from fair value remeasurements	0	$ 27
Loans
Fair Value
Gains (losses) from fair value remeasurements	8	32
Other Assets-Premises, Equipment and Software Costs
Fair Value
Gains (losses) from fair value remeasurements	(8)	(5)
Liabilities
Fair Value
Gains (losses) from fair value remeasurements	6	11
Other Liabilities and Accrued Expenses-Lending Commitments
Fair Value
Gains (losses) from fair value remeasurements	6	$ 11
Level 2
Fair Value
Loans	1,352		1,394
Other assets-Other investments			0
Other assets-Premises, equipment and software costs	0
Total assets	1,352		1,394
Other liabilities and accrued expenses-Lending commitments	173		158
Total liabilities	173		158
Level 3
Fair Value
Loans	1,057		924
Other assets-Other investments			144
Other assets-Premises, equipment and software costs	0
Total assets	1,057		1,068
Other liabilities and accrued expenses-Lending commitments	40		38
Total liabilities	$ 40		$ 38