Securities (Unrealized Gross Losses and Estimated Fair values of Investment Securities by Length of Time that Individual Securities in Each Category in Continuous Loss Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months	$ 347,651	$ 120,364
Unrealized Losses - Less Than 12 Months	(3,432)	(611)
Fair Value - 12 Months or More	192,809	307,951
Unrealized Losses - 12 Months or More	(6,709)	(7,313)
Fair Value	540,460	428,315
Unrealized Losses	(10,141)	(7,924)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	5,507	5,756
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(61)	(19)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	5,507	5,756
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	(61)	(19)
Obligations of U.S. government sponsored enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months	234,897	42,856
Unrealized Losses - Less Than 12 Months	(2,351)	(171)
Fair Value - 12 Months or More	45,629	125,439
Unrealized Losses - 12 Months or More	(1,506)	(1,834)
Fair Value	280,526	168,295
Unrealized Losses	(3,857)	(2,005)
Collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months	111,143	75,723
Unrealized Losses - Less Than 12 Months	(1,068)	(432)
Fair Value - 12 Months or More	147,180	182,512
Unrealized Losses - 12 Months or More	(5,203)	(5,479)
Fair Value	258,323	258,235
Unrealized Losses	(6,271)	(5,911)
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months	996
Unrealized Losses - Less Than 12 Months	(4)
Fair Value	996
Unrealized Losses	(4)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months	615
Unrealized Losses - Less Than 12 Months	(9)
Fair Value	615
Unrealized Losses	(9)
Private issue collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less Than 12 Months		1,785
Unrealized Losses - Less Than 12 Months		(8)
Fair Value - 12 Months or More		0
Unrealized Losses - 12 Months or More		0
Fair Value		1,785
Unrealized Losses		(8)
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	5,507	5,756
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(61)	(19)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	5,507	5,756
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (61)	$ (19)