Investment Securities (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 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	$ 553,984,000	$ 641,994,000
Unrealized Gains	17,993,000	28,342,000
Unrealized Losses	(4,366,000)	(1,797,000)
Fair Value	567,611,000	668,539,000
Interest in a limited partnership	600,000	600,000	600,000
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	551,625,000	639,616,000
Unrealized Gains	17,947,000	28,312,000
Unrealized Losses	(4,286,000)	(1,744,000)
Fair Value	565,286,000	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	73,925,000	33,955,000
Unrealized Gains	1,027,000	2,487,000
Unrealized Losses	(169,000)
Fair Value	74,783,000	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	92,920,000	135,476,000
Unrealized Gains	2,215,000	4,997,000
Unrealized Losses	(161,000)	(249,000)
Fair Value	94,974,000	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	218,569,000	278,555,000
Unrealized Gains	6,342,000	10,514,000
Unrealized Losses	(2,271,000)	(1,380,000)
Fair Value	222,640,000	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	134,112,000	164,308,000
Unrealized Gains	6,481,000	7,948,000
Unrealized Losses	(1,457,000)	(47,000)
Fair Value	139,136,000	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	19,215,000	11,964,000
Unrealized Gains	1,205,000	1,152,000
Unrealized Losses	(206,000)	(64,000)
Fair Value	20,214,000	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	12,884,000	15,358,000
Unrealized Gains	677,000	1,214,000
Unrealized Losses	(22,000)	(4,000)
Fair Value	13,539,000	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	1,395,000	1,404,000
Unrealized Gains	46,000
Unrealized Losses	(66,000)	(24,000)
Fair Value	1,375,000	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	964,000	974,000
Unrealized Gains		30,000
Unrealized Losses	(14,000)	(29,000)
Fair Value	$ 950,000	$ 975,000