Segment Information - Narrative (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 segments		Mar. 31, 2012
Segment Reporting Information [Line Items]
Net results from structured products	$ 5,176	[1]	$ 5,257	[2]
Number of segments	3
Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	5,176	[1]	5,257	[2]
Net investment income | Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	17,700		17,200
Interest expense | Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	$ (12,600)		$ (12,000)
Alternative funds
Segment Reporting Information [Line Items]
Alternative investments, timelag for reporting	1 month		1 month
Operating affiliates
Segment Reporting Information [Line Items]
Alternative investments, timelag for reporting	3 months		3 months

[1] The net results from P&C structured products include net investment income and interest expense of $17.7 million and $12.6 million, respectively

[2] The net results from P&C structured products include net investment income and interest expense of $17.2 million and $12.0 million, respectively.