Indebtedness (Trade Receivables Securitization Narrative) (Details) - Trade receivables securitization [Member] $ in Millions	Sep. 30, 2015 USD ($) banks	Jul. 24, 2015 USD ($) banks
Debt Instrument [Line Items]
Trade receivables securitization, maximum borrowing amount \| $	$ 330	$ 295
Number of commercial banks participating in trade receivables securitization agreement	4	3

Maximum borrowing amount under the trade receivables securitization without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the agreement.

No definition available.

Name:	arg_TradeReceivablesSecuritizationMaximumBorrowingAmount
Namespace Prefix:	arg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant