Schedule II - Condensed Financial Information of Registrant (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities
Net cash (used in) provided by operating activities	$ 81,048,000	$ 43,709,000	$ 44,844,000
Investing activities
Purchases of property and equipment	(1,196,000)	(1,128,000)	(3,206,000)
Net cash used in investing activities	(9,330,000)	(42,943,000)	(36,657,000)
Financing activities
Proceeds from stock option exercise	781,000	3,339,000	1,455,000
Tax benefit from share-based payments	421,000	1,043,000	238,000
Redemption of subordinated debt securities	(25,780,000)	(10,310,000)
Purchase of treasury stock		(10,268,000)	(12,102,000)
Net cash used in financing activities	(24,578,000)	(16,196,000)	(10,409,000)
Change in cash and cash equivalents	47,140,000	(15,430,000)	(2,222,000)
Cash and cash equivalents at beginning of year	45,536,000	60,966,000	63,188,000
Cash and cash equivalents at end of year	92,676,000	45,536,000	60,966,000
Parent Company [Member]
Operating activities
Net cash (used in) provided by operating activities	5,149,000	(3,646,000)	5,338,000
Investing activities
Purchases of investments	(23,361,000)	(57,148,000)	(12,491,000)
Proceeds from sales of investments	39,537,000	40,990,000	1,090,000
Purchases of property and equipment	(842,000)	(943,000)	(486,000)
Dividends from subsidiary	21,000,000	32,000,000	32,300,000
Net cash used in investing activities	36,334,000	14,899,000	20,413,000
Financing activities
Proceeds from stock option exercise	781,000	3,339,000	1,455,000
Tax benefit from share-based payments	421,000	1,043,000	238,000
Redemption of subordinated debt securities	(25,780,000)	(10,310,000)
Purchase of treasury stock		(10,268,000)	(12,102,000)
Net cash used in financing activities	(24,578,000)	(16,196,000)	(10,409,000)
Change in cash and cash equivalents	16,905,000	(4,943,000)	15,342,000
Cash and cash equivalents at beginning of year	14,887,000	19,830,000	4,488,000
Cash and cash equivalents at end of year	$ 31,792,000	$ 14,887,000	$ 19,830,000