Retirement Plans - 401(k) Retirement Savings Plan (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Employer contributions, net of forfeitures	$ 5,250	$ 4,486	$ 5,010

Defined Contribution Plan, Employer Discretionary Contribution Amount, Net of Forfeitures

No definition available.

Name:	ahs_DefinedContributionPlanEmployerDiscretionaryContributionAmountNetOfForfeitures
Namespace Prefix:	ahs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration