General - Long Term Debt and Finance Lease Obligation - Letter of Credit Agreement (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
General
Letters of credit outstanding	$ 66.4	$ 66.1

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

No definition available.

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