Junior Subordinated Debentures (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2009 Dodd-Frank Act [Member]
Junior Subordinated Debentures [Line Items]
Common stock issued by Trusts	$ 7,100,000		$ 7,200,000
Term of LIBOR variable base rate	3 months
Loss on junior subordinated debentures carried at fair value	(542,000)	(548,000)
Total assets	$ 11,491,410,000		$ 11,795,443,000	$ 15,000,000,000
Phase out period of trust preferred securities from Tier 1 to Tier 2 capital	10 years
Restricted core capital percentage	17.50%