Impairments and Other Charges (Details) - USD ($)	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Jun. 30, 2020
Impairments and Other Charges [Abstract]
Impairment charge	$ 165,304,000
Non-cash write-down	8,000,000
Changes in Goodwill [Roll Forward]
Balance (gross)	973,995,000	$ 973,995,000
Accumulated impairment and amortization	(20,169,000)	(20,169,000)
Balance	953,826,000	953,826,000
Impairment		(387,970,000)
Savage acquisition		81,667,000
Convoy acquisition		10,309,000
Balance (gross)		1,065,971,000
Accumulated impairment and amortization		(408,139,000)
Balance		657,832,000
Marine Transportation [Member]
Changes in Goodwill [Roll Forward]
Balance (gross)	424,149,000	424,149,000
Accumulated impairment and amortization	(18,574,000)	(18,574,000)
Balance	405,575,000	405,575,000
Impairment		0
Savage acquisition		81,667,000
Convoy acquisition		0
Balance (gross)		505,816,000
Accumulated impairment and amortization		(18,574,000)
Balance		487,242,000
Distribution and Services [Member]
Changes in Goodwill [Roll Forward]
Balance (gross)	549,846,000	549,846,000
Accumulated impairment and amortization	(1,595,000)	(1,595,000)
Balance	$ 548,251,000	548,251,000
Impairment		(387,970,000)
Savage acquisition		0
Convoy acquisition		10,309,000
Balance (gross)		560,155,000
Accumulated impairment and amortization		(389,565,000)
Balance		$ 170,590,000