Basis of Presentation and Summary of Significant Accounting Policies - Restricted Cash Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Trustee Deposit [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Non-current restricted cash	$ 0.7	$ 0.8
Demand Deposits [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Non-current restricted cash	$ 0.7	$ 0.7

The noncurrent cash, cash equivalents and investments that is restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits classified as long-term; that is not expected to be released from such existing restrictions within one year of the balance sheet date or operating cycle, whichever is longer. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. Includes noncurrent cash equivalents and investments that are similarly restricted as to withdrawal, usage or disposal.

No definition available.

Name:	us-gaap_RestrictedCashAndInvestmentsNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant