Employee Benefits (Retirement plan assets) (Details 4)	12 Months Ended
	Dec. 31, 2019 D
Asset allocation guidelines
Effect of market fluctuations in cash flow on target allocation limits (as a percent)	5.00%
Period during which asset allocation is expected to conform to range limits (in days)	90
S&P 500 Index
Defined benefit pension plan disclosure
Performance benchmark (as a percent)	36.00%
MSCI EAFE Index
Defined benefit pension plan disclosure
Performance benchmark (as a percent)	24.00%
Barclays Capital Aggregate Bond Index
Defined benefit pension plan disclosure
Performance benchmark (as a percent)	40.00%
Equity Securities
Defined benefit pension plan disclosure
Target plan asset allocations	60.00%
Fixed Income Securities
Defined benefit pension plan disclosure
Target plan asset allocations	40.00%
Minimum [Member]
Asset allocation guidelines
Fixed income securities, percentage of variable component in strategic targets (as a percent)	10.00%
Minimum [Member] | Equity Securities, Domestic
Defined benefit pension plan disclosure
Target plan asset allocations	50.00%
Minimum [Member] | Equity Securities, International
Defined benefit pension plan disclosure
Target plan asset allocations	0.00%
Minimum [Member] | Cash
Defined benefit pension plan disclosure
Target plan asset allocations	0.00%
Maximum [Member]
Asset allocation guidelines
Fixed income securities, percentage of variable component in strategic targets (as a percent)	20.00%
Maximum [Member] | Equity Securities, Domestic
Defined benefit pension plan disclosure
Target plan asset allocations	100.00%
Maximum [Member] | Equity Securities, International
Defined benefit pension plan disclosure
Target plan asset allocations	50.00%
Maximum [Member] | Cash
Defined benefit pension plan disclosure
Target plan asset allocations	20.00%