Investments Equity Investments (Details) - Successor [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Other investments	$ 419,896	$ 431,630
Real Estate [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	34,752	33,154
Hedge Funds, Multi-strategy [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	56,394	53,054
Interest Rate Contract [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	142,856	136,603
Illiquid Investments [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	71,366	67,787
Insurance Linked [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	23,637	22,666
Equity [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	54,682	53,675
Equity investments in pooled funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	383,687	366,939
Readily determinable fair value [Member] | Interest Rate Contract [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	$ 2,853	$ 2,823