Investments (Held-To-Maturity Securities Disclosure) (Details) (USD $)	9 Months Ended
	Sep. 30, 2012 years Securities	Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 595,600,000	$ 706,782,000
Net Unrealized Gains (Losses)	5,116,000	5,566,000
Carrying Value	600,716,000	712,348,000
Unrecognized Holding Gains	45,330,000	45,946,000
Unrecognized Holding Losses	(11,000)	(251,000)
Fixed maturity securities, held-to-maturity, fair value	646,035,000	758,043,000
Held To Maturity securities average duration	2.7
Number of held to maturity securities transferred to available-for-sale	7
Securities reclassified from the HTM category to AFS carrying value	14,600,000
Securities reclassified from the HTM category to AFS net unrecognized gain	1,200,000
Foreign Government [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	5,292,000	5,292,000
Net Unrealized Gains (Losses)	232,000	292,000
Carrying Value	5,524,000	5,584,000
Unrecognized Holding Gains	72,000	0
Unrecognized Holding Losses	0	(88,000)
Fixed maturity securities, held-to-maturity, fair value	5,596,000	5,496,000
Obligations of States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	524,807,000	614,118,000
Net Unrealized Gains (Losses)	8,261,000	11,894,000
Carrying Value	533,068,000	626,012,000
Unrecognized Holding Gains	33,438,000	31,529,000
Unrecognized Holding Losses	(11,000)	(156,000)
Fixed maturity securities, held-to-maturity, fair value	566,495,000	657,385,000
Corporate Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	49,532,000	64,840,000
Net Unrealized Gains (Losses)	(957,000)	(2,189,000)
Carrying Value	48,575,000	62,651,000
Unrecognized Holding Gains	5,048,000	6,887,000
Unrecognized Holding Losses	0	0
Fixed maturity securities, held-to-maturity, fair value	53,623,000	69,538,000
Asset-backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	7,211,000	8,077,000
Net Unrealized Gains (Losses)	(1,152,000)	(1,469,000)
Carrying Value	6,059,000	6,608,000
Unrecognized Holding Gains	1,270,000	1,353,000
Unrecognized Holding Losses	0	(7,000)
Fixed maturity securities, held-to-maturity, fair value	7,329,000	7,954,000
Commercial Mortgage-backed Securities ("CMBS") [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	8,758,000	14,455,000
Net Unrealized Gains (Losses)	(1,268,000)	(2,962,000)
Carrying Value	7,490,000	11,493,000
Unrecognized Holding Gains	5,502,000	6,177,000
Unrecognized Holding Losses	0	0
Fixed maturity securities, held-to-maturity, fair value	$ 12,992,000	$ 17,670,000