Commitments and Contingencies (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013 loan properties	Mar. 31, 2012	Dec. 31, 2012
Loss Contingencies [Line Items]
Number of non-cancelable operating leases	155
Rent expense	$ 4,700,000	$ 4,300,000
Rent income	255,000	304,000
Losses in connection with standby letters of credit	79,000	0
Standby letters of credit that expire within one year	37,000,000
Standby letters of credit that expire thereafter	18,000,000
Fair value of guarantee with standby letters of credit	213,000
Number of loans repurchased due to deficiencies in underwriting or loan documentation	20
Litigation settlement other company owned stock	4,400,000,000
Concentration risk, percentage	79.00%		79.00%
Visa Inc [Member]
Loss Contingencies [Line Items]
Other company stock owned shares	468,659
Conversion ratio from Class B shares into Class A shares	42.06%
Value of the Class A shares	$ 169.84
Unredeemed Class A equivalent shares owned	$ 33,500,000