Segment Information - Narrative (Details) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2017 USD ($)		Sep. 30, 2016 USD ($)		Sep. 30, 2017 USD ($) segments		Sep. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of segments | segments					2
Net results from structured products	$ 17,908	[1]	$ 7,708	[2]	$ 23,745	[3]	$ 11,737	[4]
Net fee income and other	(2,019)	[5]	(3,271)	[6]	(1,801)	[7]	(8,324)	[8]
Other operating expense
Segment Reporting Information [Line Items]
Net fee income and other	(13,500)		(11,900)		(37,200)		(36,000)
Total P&C | Net investment income
Segment Reporting Information [Line Items]
Net results from structured products	12,300		14,100		39,200		40,900
Total P&C | Interest expense
Segment Reporting Information [Line Items]
Net results from structured products	$ 5,600		$ (6,400)		$ (15,500)		$ (29,100)

[1] The net results from P&C structured products include net investment income and interest expense of $12.3 million and $(5.6) million, respectively.

[2] The net results from P&C structured products include net investment income and interest expense of $14.1 million and $6.4 million, respectively.

[3] The net results from P&C structured products include net investment income and interest expense of $39.2 million and $15.5 million, respectively.

[4] The net results from P&C structured products include net investment income and interest expense of $40.9 million and $29.1 million, respectively.

[5] Net fee income and other includes operating expenses of $13.5 million from the Company's loss prevention consulting services business.

[6] Net fee income and other includes operating expenses of $11.9 million from the Company's loss prevention consulting services business.

[7] Net fee income and other includes operating expenses of $37.2 million from the Company's loss prevention consulting services business.

[8] Net fee income and other includes operating expenses of $36.0 million from the Company's loss prevention consulting services business.