Segment Information - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) segments		Dec. 31, 2015 USD ($)		Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments | segments	2
Net results from structured products	$ 14,280	[1]	$ 17,991	[2]	$ 54,209	[3]
Property and casualty operations | Net Investment Income [Member]
Segment Reporting Information [Line Items]
Net results from structured products	54,000		60,400		68,000
Property and casualty operations | Interest expense
Segment Reporting Information [Line Items]
Net results from structured products	$ (39,700)		$ (42,200)		$ (12,900)

[1] The net results from P&C structured products include net investment income and interest expense of $54.0 million and $39.7 million, respectively.

[2] The net results from P&C structured products include net investment income and interest expense of $60.4 million and $42.2 million, respectively.

[3] The net results from P&C structured products include net investment income and interest expense of $68.0 million and $12.9 million, respectively.