Investment Information (Fair Value Option) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	$ 902,230		$ 917,466
Securities sold but not yet purchased	0	[1]	(6,924)	[1]
Net assets accounting for using the fair value option	902,230		910,542
Fixed Maturities
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	364,385		363,541
Other investments
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	537,845		527,971
Equity securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Investments accounted for using the fair value option	$ 0		$ 25,954

[1] Represents the Company’s obligation to deliver equity securities that it did not own at the time of sale. Such amounts are included in “other liabilities” on the Company’s consolidated balance sheets.