Employee Benefit Plans (Narrative) (Details) - Unfunded Supplemental Employee Retirement Plan (SERP) [Member] - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ 2,000,000	$ 2,000,000
Accrued benefits liabilities	$ 67,000,000		$ 66,000,000
Defined benefit plans and other post-retirement plans, weighted-average assumptions to determine net periodic cost, discount rate	4.20%	3.40%
Defined benefit plans and other post-retirement plans, weighted-average assumptions to determine net periodic cost, rate of compensation increase	3.00%	2.00%
Assets in a rabbi trust generally designated to pay benefits of the SERP	$ 78,000,000		$ 74,000,000
Defined benefit plan, noncash settlement loss	$ 0
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, noncash settlement loss		$ 1,000,000