Employee Benefits Allocation of Plan Assets (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Allocation of Plan Assets
Defined Benefit Plan, Target Plan Asset Allocations	100.00%
Defined Benefit Plan, Actual Plan Asset Allocations	100.00%	100.00%
Equity securities
Allocation of Plan Assets
Defined Benefit Plan, Target Plan Asset Allocations	24.00%
Defined Benefit Plan, Actual Plan Asset Allocations	23.00%	22.00%
Fixed income securities
Allocation of Plan Assets
Defined Benefit Plan, Target Plan Asset Allocations	29.00%
Defined Benefit Plan, Actual Plan Asset Allocations	26.00%	38.00%
Real estate
Allocation of Plan Assets
Defined Benefit Plan, Target Plan Asset Allocations	8.00%
Defined Benefit Plan, Actual Plan Asset Allocations	6.00%	7.00%
Other plan assets
Allocation of Plan Assets
Defined Benefit Plan, Target Plan Asset Allocations	39.00%
Defined Benefit Plan, Actual Plan Asset Allocations	45.00%	33.00%