Long-Term Debt Long-Term Debt - Debt Issuance Costs (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Senior Secured Credit Facility
Debt Instrument [Line Items]
Debt issuance costs	$ 1.3	$ 1.7

Amount, after accumulated amortization, of debt issuance costs related to line of credit arrangements. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section S45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68176171&loc=SL68176184-208336

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