Segment Information - Narrative (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 segments		Mar. 31, 2014
Segment Reporting Information [Line Items]
Number of segments	2
Net results from structured products	$ 5,025	[1]	$ 7,953	[2]
Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	5,025	[1]	7,953	[2]
Net investment income | Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	15,100		18,800
Interest expense | Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	$ (10,000)		$ (10,800)
Alternative funds
Segment Reporting Information [Line Items]
Alternative investments, timelag for reporting	1 month
Operating affiliates
Segment Reporting Information [Line Items]
Alternative investments, timelag for reporting	3 months

[1] The net results from P&C structured products include net investment income and interest expense of $15.1 million and $10.0 million, respectively.

[2] The net results from P&C structured products include net investment income and interest expense of $18.8 million and $10.8 million, respectively.