Commitments And Contingencies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Commitments And Contingencies [Abstract]
Other company stock owned shares	468,659
Number of non-cancelable operating leases	142
Rent expense	$ 16,600,000	$ 15,300,000	$ 13,000,000
Rent income	1,000,000	1,000,000	555,000
Losses in connection with standby letters of credit		0	23,000
Standby letters of credit losses	110,000
Standby letters of credit that expire within one year	31,500,000
Standby letters of credit that expire thereafter	29,800,000
Fair value of guarantee with standby letters of credit	254,000
Reserve for unfunded commitments	940,000	818,000	731,000
Unredeemed class A equivalent shares owned	$ 20,200,000
Concentration risk, other risk, percentage	80	82
Value of the class A shares	$ 101.53
Conversion ratio from Class B shares into Class A shares	0.4254