Hedging Activities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 Contract
Fuel Contract
Derivatives And Hedging Activities [Line Items]
Fuel hedging contracts outstanding	0
Fuel Contract | Cash Flow Hedging | Designated as Hedging Instrument
Derivatives And Hedging Activities [Line Items]
Fuel hedges expiration date	2016-12
Foreign Currency Derivatives
Derivatives And Hedging Activities [Line Items]
Foreign currency contracts outstanding	0
Foreign Currency Derivatives | Cash Flow Hedging | Designated as Hedging Instrument
Derivatives And Hedging Activities [Line Items]
Derivative instrument expiration date	2016-12