Investments Equity Investments (Details) - Successor [Member] - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Other investments	$ 394,396	$ 431,630
Real Estate [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	33,297	33,154
Hedge Funds, Multi-strategy [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	31,417	53,054
Interest Rate Contract [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	145,981	136,603
Illiquid Investments [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	67,214	67,787
Insurance Linked [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	22,023	22,666
Equity [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	56,967	53,675
Equity investments in pooled funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	356,899	366,939
Readily determinable fair value [Member] | Interest Rate Contract [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	$ 2,866	$ 2,823