Investments (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fixed Maturity Securities [Member]
Reconciliation of net unrealized investment gains (losses) on fixed maturity securities and equity securities
Beginning of period	$ 356,104	$ 163,967	$ 284,338	$ 118,498
Change in unrealized investment gains and losses	70,702	125,937	146,569	178,913
Reclassification of net realized investment (gains) losses to net income	(7,054)	(13,655)	(11,155)	(21,162)
End of period	419,752	276,249	419,752	276,249
Equity securities [Member]
Reconciliation of net unrealized investment gains (losses) on fixed maturity securities and equity securities
Beginning of period	543	2,885	2,408	2,139
Change in unrealized investment gains and losses	646	(761)	1,373	(12)
Reclassification of net realized investment (gains) losses to net income	58	(73)	(2,534)	(76)
End of period	$ 1,247	$ 2,051	$ 1,247	$ 2,051