Pension and Other Retirement Plans - Actual Allocations and Target Allocations by Asset Class (Details)	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Actual Allocations	100.00%	100.00%
Target Allocations	100.00%	100.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Actual Allocations	47.80%	52.70%
Target Allocations	50.00%	50.00%
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Actual Allocations	44.20%	40.70%
Target Allocations	45.00%	45.00%
Cash and other short-term investments
Defined Benefit Plan Disclosure [Line Items]
Actual Allocations	1.10%	0.70%
Target Allocations	0.00%	0.00%
Other alternative investments
Defined Benefit Plan Disclosure [Line Items]
Actual Allocations	6.90%	5.90%
Target Allocations	5.00%	5.00%