Commitments and Contingencies (Details)	3 Months Ended
	Mar. 31, 2016 USD ($) lawsuit individual	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Reserves for estimated uninsured losses	$ 0	$ 1,300,000
Insurance Claims
Loss Contingencies [Line Items]
Liability and cargo insurance coverage for claims	500,000
Cargo Claims
Loss Contingencies [Line Items]
Liability and cargo insurance coverage for claims	100,000
Uninsured Risk
Loss Contingencies [Line Items]
Reserves for estimated uninsured losses	$ 23,000,000	$ 25,900,000
Pending Litigation | Class Action Lawsuits In California For Alleged Violations Of Various California Labor Laws
Loss Contingencies [Line Items]
Number of class action lawsuits | lawsuit	5
Pending Litigation | Class Action Lawsuit In Illinois For Alleged Violations Of Illinois Wage Payment And Collection Act
Loss Contingencies [Line Items]
Number of class action lawsuits | lawsuit	1
Pending Litigation | Violation Of California Labor Laws
Loss Contingencies [Line Items]
Number of defendants | individual	7