Fair Value of Financial Instruments - Carrying Value and Fair Value, Senior Notes (Details) - Level 2 - Senior Unsecured Notes Effective September 2018 - Senior Notes - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Carrying value, net of unamortized debt issuance costs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	$ 2,421	$ 1,083
Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	$ 2,469	$ 1,121

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

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