Time Deposit Maturities Time Deposit Maturities (Narrative) (Details) $ in Billions	Dec. 31, 2017 USD ($)
Maturities of Time Deposits [Abstract]
Total certificates of deposit $100,000 and more	$ 2.0
Time deposits, at or above FDIC insurance limit	$ 1.0

Amount of time deposit liabilities, including certificates of deposit, in denominations that meet or exceed the Federal Deposit Insurance Corporation (FDIC) insurance limit.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=50488274&loc=d3e64164-112818

Name:	us-gaap_TimeDepositsAtOrAboveFDICInsuranceLimit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant