Securities (Summary of Investments) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale securities unrealized gains	$ 26,476		$ 29,382
Available for sale securities unrealized losses	(10,381)		(12,165)
Available for sale debt securities fair value	440,289
Total securities available for sale amortized cost	424,194	[1]	524,036	[1]
Total securities available for sale fair value	440,289		541,253
Held to maturity securities	43,569	[1]	52,139	[1]
Held to maturity securities unrealized gains	1,462		360
Held to maturity securities unrealized losses	0		0
Held to maturity securities fair value	45,031		52,499
Total available for sale and held to maturity securities amortized cost	467,763	[1]	576,175	[1]
Total available for sale and held to maturity securities unrealized gains	27,938		29,742
Total available for sale and held to maturity securities unrealized losses	(10,381)		(12,165)
Total available for sale and held to maturity securities fair value	485,320		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	29,451	[1]	29,429	[1]
Available for sale securities unrealized gains	2,584		3,404
Available for sale securities unrealized losses	0		0
Available for sale debt securities fair value	32,035		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]
Available for sale debt securities amortized cost	277,432	[1]	369,946	[1]
Available for sale securities unrealized gains	18,394		19,712
Available for sale securities unrealized losses	0		0
Available for sale debt securities fair value	295,826		389,658
Held to maturity securities	43,569	[1]	52,139	[1]
Held to maturity securities unrealized gains	1,462		360
Held to maturity securities unrealized losses	0		0
Held to maturity securities fair value	45,031		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	68,700	[1]	74,040	[1]
Available for sale securities unrealized gains	4,913		5,453
Available for sale securities unrealized losses	0		0
Available for sale debt securities fair value	73,613		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	30,667	[1]	30,639	[1]
Available for sale securities unrealized gains	0		0
Available for sale securities unrealized losses	(7,231)		(8,243)
Available for sale debt securities fair value	23,436		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	(3,117)		(3,369)
Available for sale debt securities fair value	930		887
Corporate bonds [Member]
Schedule of Available for Sale and Held to Maturity Securities [Line Items]
Available for sale debt securities amortized cost	13,897	[1]	13,872	[1]
Available for sale securities unrealized gains	585		813
Available for sale securities unrealized losses	(33)		(403)
Available for sale debt securities fair value	14,449		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.