Benefit Plans - Obligations and Funded Status (Details) - Nonqualified plan - Pension plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Change in Benefit Obligation [Roll Forward]
Benefit obligation	$ 80	$ 88
Interest cost	3	3	$ 4
Benefits paid	(5)	(7)
Actuarial (gains) losses on obligation	4	(4)
Benefit obligation	82	80	88
Amounts Recognized in Consolidated Balance Sheets [Abstract]
Accrued benefit cost	$ (82)	$ (88)	$ (88)	$ (82)	$ (80)
Accumulated other comprehensive income:
Prior service cost				0	0
Net amount recognized				$ (82)	$ (80)