Summary of Significant Accounting Policies Additional Details (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($) segment	Jan. 01, 2020 USD ($)
Accounting Policies [Abstract]
Number of operating segments | segment		1
Allowance for credit losses	$ 47,000,000	$ 47,000,000	$ 47,000,000
Write-offs charged against allowance	$ 0	$ 0