Share-Based Payments Share-based Payments - Vesting Criteria for Performance and Phantom Shares (Details)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Increase in BVPS	0.00%	5.90%	10.70%	13.30%	6.20%

Share-based Compensation Arrangement by Share-based Award, Entities That Calculate Net Asset Value Per Share, Percent

No definition available.

Name:	ahl_SharebasedCompensationArrangementbySharebasedAwardEntitiesThatCalculateNetAssetValuePerSharePercent
Namespace Prefix:	ahl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant