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Income Taxes Tax Carryforwards (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Track maintenance credit [Member]    
Tax Credit Carryforward [Line Items]    
Tax Credit Carryforward, Deferred Tax Asset 227,102,000us-gaap_TaxCreditCarryforwardDeferredTaxAsset
/ us-gaap_TaxCreditCarryforwardAxis
= gwr_ShortlinetaxcreditMember		 $ 221,278,000us-gaap_TaxCreditCarryforwardDeferredTaxAsset
/ us-gaap_TaxCreditCarryforwardAxis
= gwr_ShortlinetaxcreditMember
State and Local Jurisdiction [Member]    
Tax Credit Carryforward [Line Items]    
Operating Loss Carryforwards 387,000,000us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember		  
Minimum [Member] | Track maintenance credit [Member]    
Tax Credit Carryforward [Line Items]    
Tax Credit Carryforward, Expiration Date Jan. 01, 2026  
Minimum [Member] | State and Local Jurisdiction [Member]    
Tax Credit Carryforward [Line Items]    
Operating Loss Carryforwards, Expiration Date Jan. 01, 2015  
Maximum [Member] | Track maintenance credit [Member]    
Tax Credit Carryforward [Line Items]    
Tax Credit Carryforward, Expiration Date Dec. 31, 2034  
Maximum [Member] | State and Local Jurisdiction [Member]    
Tax Credit Carryforward [Line Items]    
Operating Loss Carryforwards, Expiration Date Dec. 31, 2034