Segment Information - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) segments		Mar. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of segments | segments	2
Net results from structured products	$ 3,411	[1]	$ 2,914	[2]
Net fee income and other	(5,742)	[3]	2,215	[4]
Other operating expense
Segment Reporting Information [Line Items]
Net fee income and other	(12,500)		(11,400)
Total P&C | Net investment income
Segment Reporting Information [Line Items]
Net results from structured products	12,300		13,400
Total P&C | Interest expense
Segment Reporting Information [Line Items]
Net results from structured products	$ (8,900)		$ (10,500)

[1] The net results from P&C structured products include net investment income and interest expense of $12.3 million and $8.9 million, respectively.

[2] The net results from P&C structured products include net investment income and interest expense of $13.4 million and $10.5 million, respectively.

[3] Net fee income and other includes operating expenses of $12.5 million from the Company's loss prevention consulting services business.

[4] Net fee income and other includes operating expenses of $11.4 million from the Company's loss prevention consulting services business.