Consolidated Statements of Changes in Members' Equity Consolidated Statements of Changes in Members' Equity (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Income tax benefit	$ 3.4	$ 0.2

Amount, after reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=118930883&loc=d3e640-108580

Name:	us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration