XML 49 R34.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Financing Obligations (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2017
Debt and Financing Obligations [Abstract] |
Schedule of Financing Obligations |
| December 31, 2017 | December 31, 2016
Revolving credit facility (a) | — |  | — |
Senior secured notes (b) | — |  | $297.6 |
Equipment financing obligations | $7.5 |  | $7.3 |
| $7.5 |  | $304.9 |
Less: Current portion of financing obligations | ($4.2 | ) | ($3.6 | )
| $3.3 |  | $301.3 |

X
- Definition Debt and Financing Obligations [Abstract] + References No definition available. + Details
Name: | agi_DebtandFinancingObligationsAbstract
Namespace Prefix: | agi_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule of Debt and Financing Obligations [Table Text Block] + References No definition available. + Details
Name: | agi_ScheduleofDebtandFinancingObligationsTableTextBlock
Namespace Prefix: | agi_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration