Commitments and Contingencies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Carrying amount of the liability for letters of credit	$ 27,000,000	$ 41,000,000
Investments in affordable housing and historic building rehabilitation projects	1,200,000,000	1,200,000,000
Commitments to fund affordable housing investments	394,000,000	334,000,000
Outstanding loan commitments for affordable housing and historic rehabilitation projects	178,000,000	135,000,000
Outstanding loan balance for affordable housing and historic rehabilitation projects	76,000,000	36,000,000
Maximum risk exposure related to affordable housing and historic rehabilitation projects	1,400,000,000	1,300,000,000
Investments in venture capital funds	261,000,000	266,000,000
Future funding commitments to venture capital funds	129,000,000	185,000,000
Loss sharing percentage with respect to certain non-agency mortgage-backed securities that Branch Bank will be reimbursed by the FDIC	95.00%
Stated threshold to measure loss share reimbursement percentage to be applied	5,000,000,000
Reimbursement percentage on losses up to the stated threshhold	80.00%
Reimbursement percentage on losses in excess of the stated threshold	95.00%
Notional/Contract amount [Member]
Letters of credit and financial guarantees written	6,095,000,000	7,291,000,000
Commitments to fund affordable housing investments	394,000,000	334,000,000
Fair value [Member]
Letters of credit and financial guarantees written	27,000,000	41,000,000
Commitments to fund affordable housing investments	$ 386,000,000	$ 316,000,000