XML 26 R78.htm IDEA: XBRL DOCUMENT v2.4.1.9
Indebtedness (Senior Notes Narrative) (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Debt Instrument [Line Items]    
Long-term debt $ 1,998,772us-gaap_LongTermDebt $ 2,107,096us-gaap_LongTermDebt
4.50% senior notes due September 2014 [Member]    
Debt Instrument [Line Items]    
Long-term debt 0us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_FourPointFivePercentSeniorNotesDueSeptemberTwoThousandFourteenMember		 399,952us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_FourPointFivePercentSeniorNotesDueSeptemberTwoThousandFourteenMember
3.25% senior notes due October 2015 [Member]    
Debt Instrument [Line Items]    
Long-term debt 249,962us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointTwoFivePercentSeniorNotesDueOctoberTwoThousandFifteenMember		 249,887us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointTwoFivePercentSeniorNotesDueOctoberTwoThousandFifteenMember
2.95% senior notes due June 2016 [Member]    
Debt Instrument [Line Items]    
Long-term debt 249,918us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_TwoPointNineFivePercentSeniorNotesMaturingJuneTwoThousandSixteenMember		 249,848us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_TwoPointNineFivePercentSeniorNotesMaturingJuneTwoThousandSixteenMember
1.65% senior notes due February 2018 [Member]    
Debt Instrument [Line Items]    
Long-term debt 324,688us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_A165SeniorNotesMaturingFebruary2018Member		 324,579us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_A165SeniorNotesMaturingFebruary2018Member
2.375% senior notes due February 2020 [Member]    
Debt Instrument [Line Items]    
Long-term debt 274,791us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_A2375SeniorNotesMaturingFebruary2020Member		 274,748us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_A2375SeniorNotesMaturingFebruary2020Member
2.90% senior notes due November 2022 [Member]    
Debt Instrument [Line Items]    
Long-term debt 249,787us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_A290SeniorNotesMaturingNovember2022Member		 249,760us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_A290SeniorNotesMaturingNovember2022Member
3.65% senior notes due July 2024 [Member]    
Debt Instrument [Line Items]    
Long-term debt 299,462us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointSixFivePercentSeniorNotesMaturingJuly2024Member		 0us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointSixFivePercentSeniorNotesMaturingJuly2024Member
Senior notes, net [Member]    
Debt Instrument [Line Items]    
Debt instrument, face amount 1,650,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 1,750,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Debt instrument, unamortized discount (1,392)us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 (1,226)us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Long-term debt 1,648,608us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 1,748,774us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Debt instrument, redemption, description the Company has the option to redeem the Senior Notes prior to their maturity, in whole or in part, at 100% of the principal plus any accrued but unpaid interest and applicable make-whole payments.  
Debt instrument, redemption price, percentage 100.00%us-gaap_DebtInstrumentRedemptionPricePercentage
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Senior notes, net [Member] | 4.50% senior notes due September 2014 [Member]    
Debt Instrument [Line Items]    
Debt instrument, interest rate, stated percentage 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= arg_FourPointFivePercentSeniorNotesDueSeptemberTwoThousandFourteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [1]  
Debt instrument, interest rate, effective percentage 4.527%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= arg_FourPointFivePercentSeniorNotesDueSeptemberTwoThousandFourteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [1]  
Debt instrument, frequency of periodic payment March 15 and September 15 [1]  
Debt instrument, face amount 0us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_FourPointFivePercentSeniorNotesDueSeptemberTwoThousandFourteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [1] 400,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_FourPointFivePercentSeniorNotesDueSeptemberTwoThousandFourteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [1]
Senior notes, net [Member] | 3.25% senior notes due October 2015 [Member]    
Debt Instrument [Line Items]    
Debt instrument, interest rate, stated percentage 3.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointTwoFivePercentSeniorNotesDueOctoberTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [2]  
Debt instrument, interest rate, effective percentage 3.283%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointTwoFivePercentSeniorNotesDueOctoberTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [2]  
Debt instrument, frequency of periodic payment April 1 and October 1 [1]  
Debt instrument, face amount 250,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointTwoFivePercentSeniorNotesDueOctoberTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [2] 250,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointTwoFivePercentSeniorNotesDueOctoberTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [2]
Senior notes, net [Member] | 2.95% senior notes due June 2016 [Member]    
Debt Instrument [Line Items]    
Debt instrument, interest rate, stated percentage 2.95%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= arg_TwoPointNineFivePercentSeniorNotesMaturingJuneTwoThousandSixteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt instrument, interest rate, effective percentage 2.98%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= arg_TwoPointNineFivePercentSeniorNotesMaturingJuneTwoThousandSixteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt instrument, frequency of periodic payment June 15 and December 15 [1]  
Debt instrument, face amount 250,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_TwoPointNineFivePercentSeniorNotesMaturingJuneTwoThousandSixteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 250,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_TwoPointNineFivePercentSeniorNotesMaturingJuneTwoThousandSixteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Senior notes, net [Member] | 1.65% senior notes due February 2018 [Member]    
Debt Instrument [Line Items]    
Debt instrument, interest rate, stated percentage 1.65%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= arg_A165SeniorNotesMaturingFebruary2018Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt instrument, interest rate, effective percentage 1.685%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= arg_A165SeniorNotesMaturingFebruary2018Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt instrument, frequency of periodic payment February 15 and August 15 [1]  
Debt instrument, face amount 325,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_A165SeniorNotesMaturingFebruary2018Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 325,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_A165SeniorNotesMaturingFebruary2018Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Senior notes, net [Member] | 2.375% senior notes due February 2020 [Member]    
Debt Instrument [Line Items]    
Debt instrument, interest rate, stated percentage 2.375%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= arg_A2375SeniorNotesMaturingFebruary2020Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt instrument, interest rate, effective percentage 2.392%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= arg_A2375SeniorNotesMaturingFebruary2020Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt instrument, frequency of periodic payment February 15 and August 15 [1]  
Debt instrument, face amount 275,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_A2375SeniorNotesMaturingFebruary2020Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 275,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_A2375SeniorNotesMaturingFebruary2020Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Senior notes, net [Member] | 2.90% senior notes due November 2022 [Member]    
Debt Instrument [Line Items]    
Debt instrument, interest rate, stated percentage 2.90%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= arg_A290SeniorNotesMaturingNovember2022Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt instrument, interest rate, effective percentage 2.913%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= arg_A290SeniorNotesMaturingNovember2022Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt instrument, frequency of periodic payment May 15 and November 15 [1]  
Debt instrument, face amount 250,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_A290SeniorNotesMaturingNovember2022Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 250,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_A290SeniorNotesMaturingNovember2022Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Senior notes, net [Member] | 3.65% senior notes due July 2024 [Member]    
Debt Instrument [Line Items]    
Debt instrument, interest rate, stated percentage 3.65%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointSixFivePercentSeniorNotesMaturingJuly2024Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [3]  
Debt instrument, interest rate, effective percentage 3.673%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointSixFivePercentSeniorNotesMaturingJuly2024Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [3]  
Debt instrument, frequency of periodic payment January 15 and July 15 [1]  
Debt instrument, face amount $ 300,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointSixFivePercentSeniorNotesMaturingJuly2024Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [3] $ 0us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= arg_ThreePointSixFivePercentSeniorNotesMaturingJuly2024Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 [3]
[1] The 2014 Notes were repaid by the Company in September 2014.
[2] The 2015 Notes are included within the “Current portion of long-term debt” line item on the Company’s consolidated balance sheet based on the maturity date.
[3] On June 17, 2014, the Company issued the 2024 Notes. The net proceeds from the sale of the 2024 Notes were used for general corporate purposes, including to fund acquisitions and repay indebtedness under the Company’s commercial paper program. Interest payments on the 2024 Notes commenced on January 15, 2015.