SCHEDULE II - Condensed Financial Information Of Registrant Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Apr. 30, 2018
Income Taxes [Line Items]
Benefit for income taxes	$ 44.7
Lower Limit \| ARX and subsidiaries
Income Taxes [Line Items]
Noncontrolling interest, ownership percentage (less than)		80.00%

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

No definition available.

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant