Retirement Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Retirement Benefits [Abstract]
Employer contribution match, percent match			100.00%	100.00%
Employer contribution match, percentage of employee contribution			6.00%	6.00%
Defined contributions plan expense	$ 4	$ 4	$ 11	$ 10
Cost or expenses included in compensation and benefit expense	$ 6	$ 5	$ 17	$ 15