Statutory Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statutory Information Table [Abstract]
Statutory policyholders' surplus	$ 2,374,420	$ 2,140,055	$ 2,207,977
Statutory net income	$ 445,999	$ 294,396	$ 387,847