Multiemployer and Defined Benefit Pension Plans (Details) $ in Millions	Sep. 30, 2017 USD ($)
American Maritime Officers Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and other postretirement benefit plans, withdrawal liability	$ 34.4

Amount of the obligation recognized by withdrawing from a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

No definition available.

Name:	us-gaap_MultiemployerPlansWithdrawalObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant