Loans and Allowance for Loan Losses (Schedule Of Impaired Loans) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	$ 13,340,000		$ 11,022,000
Recorded Investment, With allowance recorded	178,312,000		189,264,000
Recorded Investment	191,652,000		200,286,000
Unpaid Principal Balance, With no related allowance recorded	15,790,000		14,259,000
Unpaid Principal Balance, With allowance recorded	180,377,000		189,498,000
Unpaid Principal Balance	196,167,000		203,757,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	18,942,000		14,908,000
Related Allowance	18,942,000		14,908,000
Average Recorded Investment, With no related allowance recorded	11,721,000		32,314,000
Average Recorded Investment, With allowance recorded	186,410,000		190,695,000
Average Recorded Investment	198,131,000	$ 235,600,000	223,009,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	1,430,000		6,961,000
Interest Income Recognized	1,430,000	$ 0	6,961,000
Total commercial real estate
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0		56,000
Recorded Investment, With allowance recorded	49,221,000		56,840,000
Recorded Investment	49,221,000		56,896,000
Unpaid Principal Balance, With no related allowance recorded	0		1,740,000
Unpaid Principal Balance, With allowance recorded	50,961,000		56,896,000
Unpaid Principal Balance	50,961,000		58,636,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	3,740,000		4,240,000
Related Allowance	3,740,000		4,240,000
Average Recorded Investment, With no related allowance recorded	37,000		2,262,000
Average Recorded Investment, With allowance recorded	52,617,000		68,344,000
Average Recorded Investment	52,654,000		70,606,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	490,000		2,473,000
Interest Income Recognized	490,000		2,473,000
Total commercial real estate | Investment properties
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0		0
Recorded Investment, With allowance recorded	19,388,000		23,364,000
Recorded Investment	19,388,000		23,364,000
Unpaid Principal Balance, With no related allowance recorded	0		0
Unpaid Principal Balance, With allowance recorded	19,388,000		23,364,000
Unpaid Principal Balance	19,388,000		23,364,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	753,000		1,100,000
Related Allowance	753,000		1,100,000
Average Recorded Investment, With no related allowance recorded	0		123,000
Average Recorded Investment, With allowance recorded	22,769,000		28,749,000
Average Recorded Investment	22,769,000		28,872,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	198,000		1,144,000
Interest Income Recognized	198,000		1,144,000
Total commercial real estate | 1-4 family properties
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0		0
Recorded Investment, With allowance recorded	12,008,000		15,056,000
Recorded Investment	12,008,000		15,056,000
Unpaid Principal Balance, With no related allowance recorded	0		0
Unpaid Principal Balance, With allowance recorded	12,008,000		15,056,000
Unpaid Principal Balance	12,008,000		15,056,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	392,000		504,000
Related Allowance	392,000		504,000
Average Recorded Investment, With no related allowance recorded	0		323,000
Average Recorded Investment, With allowance recorded	11,715,000		16,257,000
Average Recorded Investment	11,715,000		16,580,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	216,000		925,000
Interest Income Recognized	216,000		925,000
Total commercial real estate | Land and development
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0		56,000
Recorded Investment, With allowance recorded	17,825,000		18,420,000
Recorded Investment	17,825,000		18,476,000
Unpaid Principal Balance, With no related allowance recorded	0		1,740,000
Unpaid Principal Balance, With allowance recorded	19,565,000		18,476,000
Unpaid Principal Balance	19,565,000		20,216,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	2,595,000		2,636,000
Related Allowance	2,595,000		2,636,000
Average Recorded Investment, With no related allowance recorded	37,000		1,816,000
Average Recorded Investment, With allowance recorded	18,133,000		23,338,000
Average Recorded Investment	18,170,000		25,154,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	76,000		404,000
Interest Income Recognized	76,000		404,000
Total commercial and industrial
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	9,614,000		8,220,000
Recorded Investment, With allowance recorded	103,209,000		103,114,000
Recorded Investment	112,823,000		111,334,000
Unpaid Principal Balance, With no related allowance recorded	12,039,000		9,576,000
Unpaid Principal Balance, With allowance recorded	103,532,000		103,292,000
Unpaid Principal Balance	115,571,000		112,868,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	14,405,000		9,515,000
Related Allowance	14,405,000		9,515,000
Average Recorded Investment, With no related allowance recorded	8,682,000		28,351,000
Average Recorded Investment, With allowance recorded	104,913,000		90,966,000
Average Recorded Investment	113,595,000		119,317,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	630,000		2,992,000
Interest Income Recognized	630,000		2,992,000
Total commercial and industrial | Commercial, financial and agricultural
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	9,614,000		8,220,000
Recorded Investment, With allowance recorded	65,422,000		65,715,000
Recorded Investment	75,036,000		73,935,000
Unpaid Principal Balance, With no related allowance recorded	12,039,000		9,576,000
Unpaid Principal Balance, With allowance recorded	65,691,000		65,851,000
Unpaid Principal Balance	77,730,000		75,427,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	12,491,000		7,406,000
Related Allowance	12,491,000		7,406,000
Average Recorded Investment, With no related allowance recorded	8,682,000		21,686,000
Average Recorded Investment, With allowance recorded	67,198,000		50,468,000
Average Recorded Investment	75,880,000		72,154,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	273,000		1,610,000
Interest Income Recognized	273,000		1,610,000
Total commercial and industrial | Owner-occupied
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0		0
Recorded Investment, With allowance recorded	37,787,000		37,399,000
Recorded Investment	37,787,000		37,399,000
Unpaid Principal Balance, With no related allowance recorded	0		0
Unpaid Principal Balance, With allowance recorded	37,841,000		37,441,000
Unpaid Principal Balance	37,841,000		37,441,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	1,914,000		2,109,000
Related Allowance	1,914,000		2,109,000
Average Recorded Investment, With no related allowance recorded	0		6,665,000
Average Recorded Investment, With allowance recorded	37,715,000		40,498,000
Average Recorded Investment	37,715,000		47,163,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	357,000		1,382,000
Interest Income Recognized	357,000		1,382,000
Total consumer
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	3,726,000		2,746,000
Recorded Investment, With allowance recorded	25,882,000		29,310,000
Recorded Investment	29,608,000		32,056,000
Unpaid Principal Balance, With no related allowance recorded	3,751,000		2,943,000
Unpaid Principal Balance, With allowance recorded	25,884,000		29,310,000
Unpaid Principal Balance	29,635,000		32,253,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	797,000		1,153,000
Related Allowance	797,000		1,153,000
Average Recorded Investment, With no related allowance recorded	3,002,000		1,701,000
Average Recorded Investment, With allowance recorded	28,880,000		31,385,000
Average Recorded Investment	31,882,000		33,086,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	310,000		1,496,000
Interest Income Recognized	310,000		1,496,000
Total consumer | Home equity lines
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	1,086,000		2,746,000
Recorded Investment, With allowance recorded	3,475,000		5,096,000
Recorded Investment	4,561,000		7,842,000
Unpaid Principal Balance, With no related allowance recorded	1,086,000		2,943,000
Unpaid Principal Balance, With allowance recorded	3,475,000		5,096,000
Unpaid Principal Balance	4,561,000		8,039,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	44,000		114,000
Related Allowance	44,000		114,000
Average Recorded Investment, With no related allowance recorded	2,122,000		1,205,000
Average Recorded Investment, With allowance recorded	4,383,000		7,476,000
Average Recorded Investment	6,505,000		8,681,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	45,000		334,000
Interest Income Recognized	45,000		334,000
Total consumer | Consumer mortgages
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	2,640,000		0
Recorded Investment, With allowance recorded	17,378,000		18,668,000
Recorded Investment	20,018,000		18,668,000
Unpaid Principal Balance, With no related allowance recorded	2,665,000		0
Unpaid Principal Balance, With allowance recorded	17,378,000		18,668,000
Unpaid Principal Balance	20,043,000		18,668,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	447,000		569,000
Related Allowance	447,000		569,000
Average Recorded Investment, With no related allowance recorded	880,000		496,000
Average Recorded Investment, With allowance recorded	19,106,000		19,144,000
Average Recorded Investment	19,986,000		19,640,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	194,000		896,000
Interest Income Recognized	194,000		896,000
Total consumer | Credit cards
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0		0
Recorded Investment, With allowance recorded	0		0
Recorded Investment	0		0
Unpaid Principal Balance, With no related allowance recorded	0		0
Unpaid Principal Balance, With allowance recorded	0		0
Unpaid Principal Balance	0		0
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	0		0
Related Allowance	0		0
Average Recorded Investment, With no related allowance recorded	0		0
Average Recorded Investment, With allowance recorded	0		0
Average Recorded Investment	0		0
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	0		0
Interest Income Recognized	0		0
Total consumer | Other consumer loans
Financing Receivable, Impaired [Line Items]
Recorded Investment, With no related allowance recorded	0		0
Recorded Investment, With allowance recorded	5,029,000		5,546,000
Recorded Investment	5,029,000		5,546,000
Unpaid Principal Balance, With no related allowance recorded	0		0
Unpaid Principal Balance, With allowance recorded	5,031,000		5,546,000
Unpaid Principal Balance	5,031,000		5,546,000
Related Allowance, With no related allowance recorded	0		0
Related Allowance, With allowance recorded	306,000		470,000
Related Allowance	306,000		470,000
Average Recorded Investment, With no related allowance recorded	0		0
Average Recorded Investment, With allowance recorded	5,391,000		4,765,000
Average Recorded Investment	5,391,000		4,765,000
Interest Income Recognized, With no related allowance recorded	0		0
Interest Income Recognized, With allowance recorded	71,000		266,000
Interest Income Recognized	$ 71,000		$ 266,000