Securities (Available for Sale Securities Losses) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	$ 457,582	$ 356,862
Less than 12 months, Unrealized Losses	(7,394)	(9,314)
12 months or longer, Fair Value	19,056	24,489
12 months or longer, Unrealized Losses	(722)	(914)
Total, Fair Value	476,638	381,351
Total, Unrealized Losses	(8,116)	(10,228)
U.S. Government Corporations and Agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	0	1,517
Less than 12 months, Unrealized Losses	0	(1)
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Total, Fair Value	0	1,517
Total, Unrealized Losses	0	(1)
Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	351,727	332,842
Less than 12 months, Unrealized Losses	(5,376)	(9,121)
12 months or longer, Fair Value	19,056	24,489
12 months or longer, Unrealized Losses	(722)	(914)
Total, Fair Value	370,783	357,331
Total, Unrealized Losses	(6,098)	(10,035)
Obligations of States and Political Subdivisions
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	105,855	22,503
Less than 12 months, Unrealized Losses	(2,018)	(192)
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Total, Fair Value	105,855	22,503
Total, Unrealized Losses	$ (2,018)	$ (192)