Derivative Instruments and Fair Value Measurements - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) vessel t $ / d $ / T	Dec. 31, 2018 USD ($)
High Sulfur Fuel Cost Spread
Property, Plant and Equipment [Line Items]
Derivative notional mass (metric tons) | t	38,400
High Sulfur Fuel Cost Spread | Minimum
Property, Plant and Equipment [Line Items]
Derivative contract price (usd per metric ton)	235
High Sulfur Fuel Cost Spread | Maximum
Property, Plant and Equipment [Line Items]
Derivative contract price (usd per metric ton)	250
Low Sulfur Fuel Cost Spread
Property, Plant and Equipment [Line Items]
Derivative notional mass (metric tons) | t	38,400
Low Sulfur Fuel Cost Spread | Minimum
Property, Plant and Equipment [Line Items]
Derivative contract price (usd per metric ton)	464
Low Sulfur Fuel Cost Spread | Maximum
Property, Plant and Equipment [Line Items]
Derivative contract price (usd per metric ton)	508
Bunker swaps
Property, Plant and Equipment [Line Items]
Derivative notional mass (metric tons) | t	1,100
Bunker swaps | Minimum
Property, Plant and Equipment [Line Items]
Derivative contract price (usd per metric ton)	450
Bunker swaps | Maximum
Property, Plant and Equipment [Line Items]
Derivative contract price (usd per metric ton)	487
FFAs
Property, Plant and Equipment [Line Items]
Number of days hedged | vessel	180
Vessel hire rate (usd per day) | $ / d	11,650
FFAs | Other current assets
Property, Plant and Equipment [Line Items]
Cash collateral related to derivative instruments under its collateral security arrangements | $	$ 0.6	$ 0.8