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v2.4.0.8

Related party transactions (Details) (Affiliated Entity [Member], USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Affiliated Entity [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Purchases of inventory and services | $ 5.6 | $ 5.1 | $ 4.8
Proceeds from sale of equipment and services | $ 1.1 | $ 1.1 | $ 4.0

X
- Definition Related Party Transaction, Proceeds from Sale of Inventory and Services with Related Party + References No definition available. + Details
Name: | fet_RelatedPartyTransactionProceedsFromSaleOfInventoryAndServicesWithRelatedParty
Namespace Prefix: | fet_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Related Party Transaction, Purchases of Inventory and Services with Related Party + References No definition available. + Details
Name: | fet_RelatedPartyTransactionPurchasesOfInventoryAndServicesWithRelatedParty
Namespace Prefix: | fet_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration