Loans Receivable and Allowance for Loan Losses (Schedule of Impaired Loan Receivables) (Details) (USD $)																							9 Months Ended
	Sep. 30, 2012 Impaired_Loans	Dec. 31, 2011 Impaired_Loans	Sep. 30, 2012 Commercial and industrial [Member]	Dec. 31, 2011 Commercial and industrial [Member]	Sep. 30, 2012 Commercial tax-exempt [Member]	Dec. 31, 2011 Commercial tax-exempt [Member]	Sep. 30, 2012 Owner occupied real estate [Member]	Dec. 31, 2011 Owner occupied real estate [Member]	Sep. 30, 2012 Commercial construction and land development [Member]	Dec. 31, 2011 Commercial construction and land development [Member]	Sep. 30, 2012 Commercial real estate [Member]	Dec. 31, 2011 Commercial real estate [Member]	Sep. 30, 2012 Residential [Member]	Dec. 31, 2011 Residential [Member]	Sep. 30, 2012 Consumer [Member]	Dec. 31, 2011 Consumer [Member]	Sep. 30, 2012 No Transition From Prior Year [Member]	Sep. 30, 2012 Downgraded as Impaired During the Period [Member]	Sep. 30, 2012 Downgraded as Impaired During the Period [Member] Relationships Over $1 million [Member]	Sep. 30, 2012 Downgraded as Impaired During the Period [Member] Relationships Under $1 million [Member] Impaired_Loans	Sep. 30, 2012 Upgraded as No Longer Impaired During the Period [Member]	Sep. 30, 2012 Charged Off [Member]	Sep. 30, 2012 Recategorized From Commercial Construction and Land Development to Commercial Real Estate [Member] Relationships Impaired_Loans	Sep. 30, 2012 Minimum [Member]	Sep. 30, 2012 Maximum [Member]
Loans With No Related Allowance:
Recorded Investment	$ 46,518,000	$ 49,999,000	$ 11,185,000	$ 14,504,000	$ 0	$ 0	$ 1,917,000	$ 7,000,000	$ 10,044,000	$ 11,203,000	$ 16,112,000	$ 12,117,000	$ 4,115,000	$ 3,346,000	$ 3,145,000	$ 1,829,000	$ 27,700,000
Unpaid Principal Balance	57,273,000	66,560,000	17,312,000	19,672,000	0	0	2,706,000	8,845,000	11,682,000	19,756,000	17,836,000	12,390,000	4,375,000	3,729,000	3,362,000	2,168,000
Loans With An Allowance Recorded:
Recorded Investment	17,654,000	13,505,000	7,549,000	1,000,000			2,241,000	492,000	7,864,000	12,013,000							11,100,000
Unpaid Principal Balance	18,654,000	13,672,000	8,549,000	1,000,000			2,241,000	659,000	7,864,000	12,013,000
Total Impaired Loans:
Recorded Investment	64,172,000	63,504,000	18,734,000	15,504,000	0	0	4,158,000	7,492,000	17,908,000	23,216,000	16,112,000	12,117,000	4,115,000	3,346,000	3,145,000	1,829,000		15,400,000	5,400,000	8,000,000		5,000,000	4,500,000
Bank loans receivable, Gross	1,504,990,000	1,436,668,000	347,099,000	321,988,000	88,934,000	81,532,000	274,235,000	279,372,000	107,311,000	103,153,000	393,182,000	364,405,000	82,989,000	83,940,000	211,240,000	202,278,000					9,300,000
Unpaid Principal Balance	75,927,000	80,232,000	25,861,000	20,672,000	0	0	4,947,000	9,504,000	19,546,000	31,769,000	17,836,000	12,390,000	4,375,000	3,729,000	3,362,000	2,168,000
Related Allowance	8,358,000	3,630,000	4,161,000	1,000,000	0	0	1,747,000	30,000	2,450,000	2,600,000	0	0	0	0	0	0
Number of impaired loans	8	4																		55			2
Number of impaired receivable relationships																							1
Impaired financing receivable, classification of relationship, value																								$ 1,000,000	$ 1,000,000