Investment Information (Net Investment Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Net investment income:
Gross investment income	$ 74,337		$ 80,978
Investment expenses	(8,665)		(6,681)
Net investment income	65,672		74,297
Fixed Maturities
Net investment income:
Gross investment income	62,006		73,450
Term loan investments
Net investment income:
Gross investment income	4,217	[1]	2,299	[1]
Short-term investments
Net investment income:
Gross investment income	392		372
Equity securities
Net investment income:
Gross investment income	1,423		1,664
Other
Net investment income:
Gross investment income	$ 6,299	[2]	$ 3,193	[2]

[1] Included in “investments accounted for using the fair value option” on the Company’s consolidated balance sheets.

[2] Amounts include dividends on investment funds and other items.