Related Party Transactions - Schedule of Related Party Expenses Including Personnel Costs (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transactions [Abstract]
Operations and maintenance – related parties	$ 54.4	$ 45.6	$ 40.0
General and administrative – related parties	$ 51.7	$ 47.7	$ 43.7

Costs of sales and operating expenses for the period incurred from transactions with related parties.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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