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Long-Term Debt (Narrative) (Details) (USD $)
 3 Months Ended 0 Months Ended 6 Months Ended
Mar. 31, 2015
Jul. 16, 2014
Jul. 15, 2014
Dec. 31, 2014
Nov. 20, 2012
May 28, 2010
Fixed Interest Rate [Member]            
Schedule of Capitalization, Long-term Debt [Line Items]            
Long-term Debt 1,383,600,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= amsg_FixedInterestRateMember		          
Long-term Debt, Fair Value 1,419,300,000us-gaap_LongTermDebtFairValue
/ us-gaap_DebtInstrumentAxis
= amsg_FixedInterestRateMember		          
Variable Interest Rate [Member]            
Schedule of Capitalization, Long-term Debt [Line Items]            
Long-term Debt, Fair Value 865,300,000us-gaap_LongTermDebtFairValue
/ us-gaap_DebtInstrumentAxis
= amsg_VariableInterestRateMember		          
5.625% Senior Unsecured Notes due 2020 [Member] | Senior Notes [Member]            
Schedule of Capitalization, Long-term Debt [Line Items]            
Long-term Debt 250,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentySeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		     250,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentySeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		    
Senior Unsecured Debt            
Face amount         250,000,000.0us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentySeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Interest rate         5.625%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentySeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Redeemable principal percentage 35.00%amsg_RedeemablePrincipalPercentage
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentySeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		          
Senior Secured Debt            
Face amount         250,000,000.0us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentySeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Interest rate         5.625%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentySeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
5.625% Senior Unsecured Notes due 2022 [Member] | Senior Notes [Member]            
Schedule of Capitalization, Long-term Debt [Line Items]            
Long-term Debt 1,100,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentyTwoSeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		     1,100,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentyTwoSeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		    
Senior Unsecured Debt            
Face amount   1,100,000,000.0us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentyTwoSeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		        
Interest rate   5.625%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentyTwoSeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		        
Redeemable principal percentage 35.00%amsg_RedeemablePrincipalPercentage
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentyTwoSeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		          
Senior Secured Debt            
Face amount   1,100,000,000.0us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentyTwoSeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		        
Interest rate   5.625%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentyTwoSeniorUnsecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		        
8.04% Senior Secured Notes due 2020 [Member] | Senior Notes [Member]            
Senior Unsecured Debt            
Face amount           75,000,000.0us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentySeniorSecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Senior Secured Debt            
Face amount           75,000,000.0us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentySeniorSecuredNotesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Period Prior to November 30, 2015 [Member] | 5.625% Senior Unsecured Notes due 2020 [Member] | Senior Notes [Member]            
Senior Unsecured Debt            
Redemption price as percent of the principal amount 105.625%us-gaap_DebtInstrumentRedemptionPricePercentage
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentySeniorUnsecuredNotesMember
/ us-gaap_DebtInstrumentRedemptionPeriodAxis
= us-gaap_DebtInstrumentRedemptionPeriodOneMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		          
Period Prior to July 15, 2017 [Member] | 5.625% Senior Unsecured Notes due 2022 [Member] | Senior Notes [Member]            
Senior Unsecured Debt            
Redemption price as percent of the principal amount 105.625%us-gaap_DebtInstrumentRedemptionPricePercentage
/ us-gaap_DebtInstrumentAxis
= amsg_TwoThousandTwentyTwoSeniorUnsecuredNotesMember
/ us-gaap_DebtInstrumentRedemptionPeriodAxis
= amsg_DebtInstrumentRedemptionPeriodSixMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		          
Senior Secured Credit Facility - Term Loan [Member]            
Term Loan and Credit Facility            
Borrowing capacity of new revolving credit agreement   870,000,000.0us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= amsg_SeniorSecuredCreditFacilityTermLoanMember		        
Quarterly principal payment as a percent of face amount   0.25%amsg_DebtInstrumentPeriodicPaymentPercentofPrincipal
/ us-gaap_CreditFacilityAxis
= amsg_SeniorSecuredCreditFacilityTermLoanMember		        
Annual principal payment   8,700,000us-gaap_DebtInstrumentAnnualPrincipalPayment
/ us-gaap_CreditFacilityAxis
= amsg_SeniorSecuredCreditFacilityTermLoanMember		        
Revolving Credit Facility [Member]            
Term Loan and Credit Facility            
Borrowing capacity of new revolving credit agreement   300,000,000.0us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember		 475,000,000.0us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember		      
Unused capacity commitment fee, percentage   0.375%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember		        
Senior Secured Credit Facility [Member]            
Term Loan and Credit Facility            
Maximum increase in borrowing capacity   $ 300,000,000.0amsg_LineofCreditFacilityMaximumIncreaseinBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= amsg_SeniorSecuredCreditFacilityMember		        
Base Rate [Member] | Senior Secured Credit Facility - Term Loan [Member] | Maximum [Member]            
Term Loan and Credit Facility            
Basis spread   2.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= amsg_SeniorSecuredCreditFacilityTermLoanMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember		        
Base Rate [Member] | Senior Secured Credit Facility - Term Loan [Member] | Minimum [Member]            
Term Loan and Credit Facility            
Basis spread   1.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= amsg_SeniorSecuredCreditFacilityTermLoanMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember		        
Base Rate [Member] | Revolving Credit Facility [Member] | Maximum [Member]            
Term Loan and Credit Facility            
Basis spread   2.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember		 1.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember		      
Base Rate [Member] | Revolving Credit Facility [Member] | Minimum [Member]            
Term Loan and Credit Facility            
Basis spread   1.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember		 0.25%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_BaseRateMember		      
LIBOR [Member] | Senior Secured Credit Facility - Term Loan [Member]            
Term Loan and Credit Facility            
Floor rate   0.75%amsg_DebtInstrumentVariableRateFloor
/ us-gaap_CreditFacilityAxis
= amsg_SeniorSecuredCreditFacilityTermLoanMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		        
Current variable rate 3.75%amsg_DebtInstrumentCurrentVariableRate
/ us-gaap_CreditFacilityAxis
= amsg_SeniorSecuredCreditFacilityTermLoanMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		          
LIBOR [Member] | Senior Secured Credit Facility - Term Loan [Member] | Maximum [Member]            
Term Loan and Credit Facility            
Basis spread   3.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= amsg_SeniorSecuredCreditFacilityTermLoanMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		        
LIBOR [Member] | Senior Secured Credit Facility - Term Loan [Member] | Minimum [Member]            
Term Loan and Credit Facility            
Basis spread   2.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= amsg_SeniorSecuredCreditFacilityTermLoanMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		        
LIBOR [Member] | Revolving Credit Facility [Member] | Maximum [Member]            
Term Loan and Credit Facility            
Basis spread   3.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		 2.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		      
LIBOR [Member] | Revolving Credit Facility [Member] | Minimum [Member]            
Term Loan and Credit Facility            
Basis spread   2.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		 1.25%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember