Summary of Significant Accounting Policies Investments (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($)
Receivables [Abstract]
Available-for-sale Securities	$ 5
Par value	$ 19

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with interest rate reset through auction process, sold at par value.

No definition available.

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