Securities (Summary of Investments) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Unrealized Gains	$ 21,209		$ 29,382
Securities Available for Sale, Unrealized Losses	(9,119)		(12,165)
Securities Available for Sale, Fair Value	375,498
Total securities available for sale, Amortized Cost	363,408	[1]	524,036	[1]
Total securities available for sale, Fair Value	375,498		541,253
Securities Held to Maturity, Amortized Cost	40,381	[1]	52,139	[1]
Securities Held to Maturity, Unrealized Gains	1,039		360
Securities Held to Maturity, Unrealized Losses	0		0
Securities Held to Maturity, Fair Value	41,420		52,499
Total securities, Amortized Cost	403,789	[1]	576,175	[1]
Total securities, Unrealized Gains	22,248		29,742
Total securities, Unrealized Losses	(9,119)		(12,165)
Total securities, Fair Value	416,918		593,752
Obligations of U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	29,458	[1]	29,429	[1]
Securities Available for Sale, Unrealized Gains	2,212		3,404
Securities Available for Sale, Unrealized Losses	0		0
Securities Available for Sale, Fair Value	31,670		32,833
Mortgage-backed securities issued by U.S. government-sponsored agencies and U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	217,136	[1]	369,946	[1]
Securities Available for Sale, Unrealized Gains	14,097		19,712
Securities Available for Sale, Unrealized Losses	0		0
Securities Available for Sale, Fair Value	231,233		389,658
Securities Held to Maturity, Amortized Cost	40,381	[1]	52,139	[1]
Securities Held to Maturity, Unrealized Gains	1,039		360
Securities Held to Maturity, Unrealized Losses	0		0
Securities Held to Maturity, Fair Value	41,420		52,499
States and political subdivisions [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	68,196	[1]	74,040	[1]
Securities Available for Sale, Unrealized Gains	4,424		5,453
Securities Available for Sale, Unrealized Losses	0		0
Securities Available for Sale, Fair Value	72,620		79,493
Trust preferred securities: Individual name issuers [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	30,677	[1]	30,639	[1]
Securities Available for Sale, Unrealized Gains	0		0
Securities Available for Sale, Unrealized Losses	(5,926)		(8,243)
Securities Available for Sale, Fair Value	24,751		22,396
Trust preferred securities: Collateralized debt obligations [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	4,036	[1]	4,256	[1]
Securities Available for Sale, Unrealized Gains	0		0
Securities Available for Sale, Unrealized Losses	(3,193)		(3,369)
Securities Available for Sale, Fair Value	843		887
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Amortized Cost	13,905	[1]	13,872	[1]
Securities Available for Sale, Unrealized Gains	476		813
Securities Available for Sale, Unrealized Losses	0		(403)
Securities Available for Sale, Fair Value	14,381		14,282
Perpetual preferred stock [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Securities Available for Sale, Unrealized Gains			0	[2]
Securities Available for Sale, Unrealized Losses			(150)	[2]
Securities Available for Sale, Equity Securities, Amortized Cost			1,854	[1],[2]
Securities Available for Sale, Equity Securities, Fair Value			$ 1,704	[2]

[1] Net of other-than-temporary impairment losses.

[2] Callable at the discretion of the issuer.