Segment Information - Narrative (Details) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2017 USD ($)		Jun. 30, 2016 USD ($)		Jun. 30, 2017 USD ($) segments		Jun. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of segments | segments					2
Net results from structured products	$ 2,923	[1]	$ 2,059	[2]	$ 5,837	[3]	$ 4,029	[4]
Net fee income and other	(1,997)	[5]	(2,330)	[6]	218	[7]	(5,053)	[8]
Net investment income | Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	13,500		14,100		26,900		26,700
Interest Expense [Member] | Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	(10,600)		(12,000)		(21,100)		(22,700)
Other Operating Income (Expense) [Member]
Segment Reporting Information [Line Items]
Net fee income and other	$ (12,200)		$ (13,200)		$ (23,700)		$ (24,200)

[1] The net results from P&C structured products include net investment income and interest expense of $13.5 million and $10.6 million, respectively.

[2] The net results from P&C structured products include net investment income and interest expense of $14.1 million and $12.0 million, respectively.

[3] The net results from P&C structured products include net investment income and interest expense of $26.9 million and $21.1 million, respectively.

[4] The net results from P&C structured products include net investment income and interest expense of $26.7 million and $22.7 million, respectively.

[5] Net fee income and other includes operating expenses of $12.2 million from the Company's loss prevention consulting services business.

[6] Net fee income and other includes operating expenses of $13.2 million from the Company's loss prevention consulting services business.

[7] Net fee income and other includes operating expenses of $23.7 million from the Company's loss prevention consulting services business.

[8] Net fee income and other includes operating expenses of $24.2 million from the Company's loss prevention consulting services business.