Securities (Summary of Investments) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities unrealized gains	$ 26,854		$ 29,382
Available for sale securities unrealized losses	(10,420)		(12,165)
Available for sale debt securities fair value	469,167
Total securities available for sale amortized cost	452,733	[1]	524,036	[1]
Total securities available for sale fair value	469,167		541,253
Held to maturity securities	47,026	[1]	52,139	[1]
Held to maturity securities unrealized gains	1,194		360
Held to maturity securities unrealized losses	0		0
Held to maturity securities fair value	48,220		52,499
Total available for sale and held to maturity securities amortized cost	499,759	[1]	576,175	[1]
Total available for sale and held to maturity securities unrealized gains	28,048		29,742
Total available for sale and held to maturity securities unrealized losses	(10,420)		(12,165)
Total available for sale and held to maturity securities fair value	517,387		593,752
Obligations of U.S. government-sponsored enterprises [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities amortized cost	29,443	[1]	29,429	[1]
Available for sale securities unrealized gains	2,876		3,404
Available for sale securities unrealized losses	0		0
Available for sale debt securities fair value	32,319		32,833
Held to maturity securities	47,026
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]
Available for sale debt securities amortized cost	305,757	[1]	369,946	[1]
Available for sale securities unrealized gains	18,535		19,712
Available for sale securities unrealized losses	0		0
Available for sale debt securities fair value	324,292		389,658
Held to maturity securities	47,026	[1]	52,139	[1]
Held to maturity securities unrealized gains	1,194		360
Held to maturity securities unrealized losses	0		0
Held to maturity securities fair value	48,220		52,499
States and political subdivisions [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities amortized cost	68,939	[1]	74,040	[1]
Available for sale securities unrealized gains	4,784		5,453
Available for sale securities unrealized losses	0		0
Available for sale debt securities fair value	73,723		79,493
Trust preferred securities: Individual name issuers [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities amortized cost	30,658	[1]	30,639	[1]
Available for sale securities unrealized gains	0		0
Available for sale securities unrealized losses	(7,038)		(8,243)
Available for sale debt securities fair value	23,620		22,396
Trust preferred securities: Collateralized debt obligations [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities amortized cost	4,047	[1]	4,256	[1]
Available for sale securities unrealized gains	0		0
Available for sale securities unrealized losses	(3,280)		(3,369)
Available for sale debt securities fair value	767		887
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities amortized cost	13,889	[1]	13,872	[1]
Available for sale securities unrealized gains	659		813
Available for sale securities unrealized losses	(102)		(403)
Available for sale debt securities fair value	14,446		14,282
Perpetual preferred stock [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities unrealized gains			0	[2]
Available for sale securities unrealized losses			(150)	[2]
Available for sale equity securities amortized cost			1,854	[1],[2]
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.