Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2021

Commitments and Contingencies Disclosure [Abstract]

Schedule of Schedule of Changes in Contract Obligations

The changes in contract obligations are as follows:

	Nine Months Ended September 30, 2021
	(in millions)
Beginning contract obligations	$	360
Liabilities settled	(159)
Accretion of discount	6
Changes in estimate (a)	(2)
Ending contract obligations	$	205

______________________

(a)Represents differences between estimated and actual liabilities settled.