Summary of Significant Accounting Policies, Goodwill and Other Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 14, 2018
Goodwill [Abstract]
Impairment of goodwill	$ 2,702	$ 0	$ 0
Gross carrying value of goodwill	973,995	947,502
Accumulated amortization	15,566	15,566
Accumulated impairment losses	4,603	1,901
Net goodwill	953,826	935,135		$ 4,657
Other Intangibles [Abstract]
Intangible assets gross carrying amounts	326,984	315,983
Intangible assets accumulated amortization	102,787	83,175
Intangible assets net carrying amount	224,197	232,808
Intangible liabilities gross carrying value	18,323	7,437
Intangible liabilities accumulated amortization	8,652	4,751
Intangible liabilities net carrying amount	9,671	2,686
Amortization of intangible assets	16,760	11,296	$ 8,467
Intangible Assets and liabilities, Estimated Amortization Expense, Fiscal Year Maturity [Abstract]
2018	18,999
2019	20,854
2020	20,174
2021	19,824
2022	$ 19,782
Weighted average amortization period for intangible assets and liabilities	14 years
Marine Transportation Segment [Member]
Goodwill [Abstract]
Net goodwill	$ 405,575	387,504
Distribution and Services Segment [Member]
Goodwill [Abstract]
Net goodwill	$ 548,251	$ 547,631