Commitments And Contingencies (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010
Loss Contingencies [Line Items]
Number of non-cancelable operating leases	143
Rent expense	$ 4,200,000	$ 4,100,000
Rent income	304,000	272,000
Standby letters of credit that expire within one year	26,100,000
Standby letters of credit that expire thereafter	35,100,000
Fair value of guarantee with standby letters of credit	285,000
Reserve for unfunded commitments	1,102,000	911,000	940,000	818,000
Other company stock owned shares	468,659
Value of the Class A shares, per share	118.00
Concentration risk, other risk	80.00%
Visa Inc [Member]
Loss Contingencies [Line Items]
Conversion ratio from Class B shares into Class A shares	0.42540
Unredeemed Class A equivalent shares owned	$ 23,500,000