Shareholders' Equity (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	$ 227,659
Other Comprehensive Income Loss Net Of Tax	67,612	130,473	(22,479)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	295,271	227,659
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	213,114	82,673	97,108
Other Comprehensive Income Loss Net Of Tax	69,389	130,441	(14,435)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	282,503	213,114	82,673
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	14,545	14,513	22,557
Other Comprehensive Income Loss Net Of Tax	(1,777)	32	(8,044)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	12,768	14,545	14,513
Accumulated other comprehensive income
Other Comprehensive Income Loss Net Of Tax	$ 67,612	$ 130,473	$ (22,479)