Investment Securities (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Cost/amortized cost, unrealized gains and losses, and fair value of investment securities by type, which are classified as available-for-sale
Cost/Amortized Cost	$ 612,602,000	$ 641,994,000
Unrealized Gains	28,125,000	28,342,000
Unrealized Losses	(1,668,000)	(1,797,000)
Fair Value	639,059,000	668,539,000
Interest in a limited partnership	600,000	600,000	1,400,000
Investment securities with other-than-temporary impairments recognized in accumulated other comprehensive income or loss	0	0
Bonds:
Cost/amortized cost, unrealized gains and losses, and fair value of investment securities by type, which are classified as available-for-sale
Cost/Amortized Cost	610,222,000	639,616,000
Unrealized Gains	28,077,000	28,312,000
Unrealized Losses	(1,584,000)	(1,744,000)
Fair Value	636,715,000	666,184,000
U.S. government and government sponsored entities
Cost/amortized cost, unrealized gains and losses, and fair value of investment securities by type, which are classified as available-for-sale
Cost/Amortized Cost	36,586,000	33,955,000
Unrealized Gains	2,253,000	2,487,000
Fair Value	38,839,000	36,442,000
Obligations of states, municipalities, and political subdivisions
Cost/amortized cost, unrealized gains and losses, and fair value of investment securities by type, which are classified as available-for-sale
Cost/Amortized Cost	125,172,000	135,476,000
Unrealized Gains	4,630,000	4,997,000
Unrealized Losses	(269,000)	(249,000)
Fair Value	129,533,000	140,224,000
Corporate debt
Cost/amortized cost, unrealized gains and losses, and fair value of investment securities by type, which are classified as available-for-sale
Cost/Amortized Cost	256,279,000	278,555,000
Unrealized Gains	10,135,000	10,514,000
Unrealized Losses	(1,035,000)	(1,380,000)
Fair Value	265,379,000	287,689,000
RMBS
Cost/amortized cost, unrealized gains and losses, and fair value of investment securities by type, which are classified as available-for-sale
Cost/Amortized Cost	160,253,000	164,308,000
Unrealized Gains	8,573,000	7,948,000
Unrealized Losses	(271,000)	(47,000)
Fair Value	168,555,000	172,209,000
CMBS
Cost/amortized cost, unrealized gains and losses, and fair value of investment securities by type, which are classified as available-for-sale
Cost/Amortized Cost	13,866,000	11,964,000
Unrealized Gains	1,354,000	1,152,000
Unrealized Losses	(9,000)	(64,000)
Fair Value	15,211,000	13,052,000
CDO/ABS
Cost/amortized cost, unrealized gains and losses, and fair value of investment securities by type, which are classified as available-for-sale
Cost/Amortized Cost	18,066,000	15,358,000
Unrealized Gains	1,132,000	1,214,000
Unrealized Losses		(4,000)
Fair Value	19,198,000	16,568,000
Other long-term investments
Cost/amortized cost, unrealized gains and losses, and fair value of investment securities by type, which are classified as available-for-sale
Cost/Amortized Cost	1,405,000	1,404,000
Unrealized Gains	2,000
Unrealized Losses	(67,000)	(24,000)
Fair Value	1,340,000	1,380,000
Common stocks
Cost/amortized cost, unrealized gains and losses, and fair value of investment securities by type, which are classified as available-for-sale
Cost/Amortized Cost	975,000	974,000
Unrealized Gains	46,000	30,000
Unrealized Losses	(17,000)	(29,000)
Fair Value	$ 1,004,000	$ 975,000