Variable Interest Entities (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) director	Feb. 05, 2018 USD ($)	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured	15.00%		15.00%
HG Global
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured				15.00%
BAM
Variable Interest Entity [Line Items]
Right to elect directors on board number | director	2
First Loss Reinsurance Treaty | HG Global
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured	15.00%
First Loss Reinsurance Treaty | BAM
Variable Interest Entity [Line Items]
Percentage of premiums	60.00%
Other long-term investments | Kudu
Variable Interest Entity [Line Items]
Unfunded capital commitment		$ 125.0
VIE, carrying amount	$ 30.7