Related Party Transactions Narrative (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2016 USD ($) shares
Related Party Transaction [Line Items]
Treasury Stock, Value, Acquired, Cost Method	$ 42,532
Mariner Invesment Group LLC
Related Party Transaction [Line Items]
Management Fee, Percentage of Company's Net Assets	0.025%
Successive terms (in years)	1 year
Notice period (in days)	60 days
Treasury Stock | Common Stock - Class A
Related Party Transaction [Line Items]
Treasury Stock, Shares, Acquired | shares	6,596,000
Treasury Stock, Value, Acquired, Cost Method	$ 42,524
Treasury Stock | Common Stock - Class A | ProSight Specialty Insurance Group, Inc. [Member]
Related Party Transaction [Line Items]
Treasury Stock, Shares, Acquired | shares	5,596,000
Treasury Stock, Value, Acquired, Cost Method	$ 36,374
Treasury Stock | Common Stock - Class A | NOMURA SECURITIES CO LTD [Member]
Related Party Transaction [Line Items]
Treasury Stock, Shares, Acquired | shares	1,000,000
Treasury Stock, Value, Acquired, Cost Method	$ 6,150