Supplemental Reinsurance Premiums (Schedule of Property and Liability Insurance Earned Premiums) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Supplementary Insurance Information [Abstract]
Direct amounts									$ 2,704,401	$ 2,578,715	$ 2,569,661
Ceded to other companies									(7,059)	(5,066)	(4,134)
Assumed									845	1,271	530
Net amounts	$ 680,892	$ 678,913	$ 675,787	$ 662,595	$ 655,777	$ 646,084	$ 637,247	$ 635,812	$ 2,698,187	$ 2,574,920	$ 2,566,057