Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Schedule of Fair Values of Financial Instruments and Nonfinancial Assets and Liabilities Measured at the Reporting Date

The fair values of these financial instruments are summarized as follows:

			Fair Value Measurements at Reporting Date Using
Description	At December 31, 2018		QuotedPrices in Active Markets for Identical Assets (Level 1)		SignificantOther Observable Inputs (Level 2)		Significant UnobservableInputs (Level 3)
Fuel hedge contracts	$	4,710	$	—	$	4,710	$	—
			Fair Value Measurements at Reporting Date Using
Description	At December 31, 2017		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Fuel hedge contracts	$	2,501	$	—	$	2,501	$	—

Schedule of Fair Value of Fuel Hedge Contracts Balance Sheet Location

The fair value of the fuel hedge contracts outstanding as of December 31, 2018 and 2017 is as follows:

	Balance Sheet Location	Fair Value at December 31,
		2018		2017
Asset derivatives:
Derivatives designated as hedging instruments
Fuel hedge contracts	Other current assets	$	—	$	2,501
Liability derivatives:
Derivatives designated as hedging instruments
Fuel hedge contracts	Accrued expenses	$	4,710	$	—

Changes in Components of Accumulated Other Comprehensive Income (Loss)

Changes in the components of the accumulated balances of other comprehensive income (loss) are as follows:

		2018			2017			2016
Cumulative translation adjustments—net of tax	$	1,513		$	(41	)	$	508
Derivatives:
Reclassification of derivative (gains) losses to earnings—net of tax		(1,569	)		(218	)		30
Change in fair value of derivatives—net of tax		(3,756	)		1,407			300
Net unrealized (gain) loss on derivatives—net of tax		(5,325	)		1,189			330
Total other comprehensive income (loss)	$	(3,812	)	$	1,148		$	838

Adjustments Reclassified from Accumulated Balances Other Comprehensive Income (Loss) to Earnings

Adjustments reclassified from accumulated balances of other comprehensive income (loss) to earnings are as follows:

	Statement of Operations Location		2018			2017			2016
Derivatives:
Fuel hedge contracts	Costs of contract revenues	$	(2,125	)	$	(358	)	$	50
	Income tax (provision) benefit		(556	)		140			20
		$	(1,569	)	$	(218	)	$	30

Adjustments reclassified from accumulated balances of other comprehensive income (loss) to earnings are as follows:

	Statement of Operations Location		2018			2017		2016
Cumulative translation adjustment:	Other expense	$	(2,337	)	$	—	$	—
	Income tax benefit		612			—		—
		$	(1,725	)	$	—	$	—