Retirement Plans and Other Benefits - Projected Benefit Obligation for Pension Plans (Details) - Pension Benefits - USD ($) $ in Thousands |
Dec. 31, 2018 |
Dec. 31, 2017 |
---|---|---|
Projected benefit obligation and the accumulated benefit obligation for pension plans with an accumulated obligation in excess of plan assets | ||
Projected benefit obligation | $ 3,190,626 | $ 3,394,186 |
Accumulated benefit obligation | 3,038,774 | 3,227,233 |
Fair value of plan assets | $ 2,733,476 | $ 3,057,027 |