Accounting Policies (Details) - USD ($)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Charge off threshold - small business commercial loans	$ 1,000,000
Derecognition of ALLL associated with purchased impaired loans	468,000,000
Effect of adopting ASU 2015-07 [Member] \| Indirect Investments Equity [Member] \| Level 3 [Member]
Equity investments	$ 347,000,000	$ 469,000,000

Fair value of investments in certain entities that calculate net asset value per share, including, but not limited to, by unit, membership interest, or other ownership interest. Investments include, but are not limited to, investments in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=SL6742756-110258

Name:	us-gaap_AlternativeInvestmentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant