Retirement Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Retirement Benefits [Abstract]
Employer contribution match, percent match	100.00%
Employer contribution match, percentage of employee contribution	6.00%
Defined contributions plan expense	$ 4	$ 3
Cost or expenses included in compensation and benefit expense	$ 5	$ 5