Pension plan and 401(k) Program - Asset Allocation by Percentage of Plan Asset Category (Details)	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, allocation percentage	100.00%	100.00%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, allocation percentage	37.90%	34.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, allocation percentage	33.20%	32.40%
Real estate
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, allocation percentage	15.40%	4.30%
Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, allocation percentage	12.90%	27.30%
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, allocation percentage	0.60%	2.00%