Pension Plans - Non-Qualified Plans (Details) - Non-Qualified Plan [Member] $ in Millions	Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, type	us-gaap:PensionPlansDefinedBenefitMember
Defined benefit plan, funding status	us-gaap:UnfundedPlanMember
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Plan with accumulated benefit obligation in excess of plan assets, accumulated benefit obligation	$ 13.7
Plan with accumulated benefit obligation in excess of plan assets, projected benefit obligation	13.7
Defined Benefit Plan, Pension Plan with Project Benefit Obligation in Excess of Plan Assets [Abstract]
Plan with projected benefit obligation in excess of plan assets, accumulated benefit obligation	13.7
Plan with projected benefit obligation in excess of plan assets, projected benefit obligation	$ 13.7