Retirement Benefits - Obligations and Funded Status (Details) - USD ($) $ in Millions | Oct. 08, 2019 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 |
Total | | | | |
Changes in the benefit obligation [Roll Forward] | | | | |
Benefit obligation at beginning of year | | $ 1,145.2 | $ 1,066.1 | |
Service cost | | 9.7 | 9.9 | $ 10.5 |
Interest cost | | 38.3 | 44.5 | 43.7 |
Participant contributions | | 0.7 | 0.1 | |
Plan amendments | | 0.3 | (0.6) | |
Plan combinations | | 1 | 1.4 | |
Acquisitions | | 132.5 | | |
Curtailment | | (1.5) | (0.8) | |
Settlements | | (0.7) | (54.5) | |
Benefits paid | | (65.6) | (67.3) | |
Actuarial losses | | 141.4 | 136.7 | |
Foreign currency exchange effects | | 26.5 | 9.7 | |
Benefit obligation at end of year | | 1,427.8 | 1,145.2 | 1,066.1 |
Changes in plan assets [Roll Forward] | | | | |
Fair value of plan assets at beginning of year | | 914.4 | 867.2 | |
Return on assets – actual | | 140.3 | 143.3 | |
Participant contributions | | 0.7 | 0.1 | |
Plan combinations | | 1 | 1.4 | |
Employer contributions | | 14.8 | 14.6 | |
Acquisitions | | 80.3 | | |
Settlements | | (0.7) | (53.9) | |
Benefits paid | | (65.6) | (67.3) | |
Foreign currency exchange effects | | 17.7 | 9 | |
Fair value of plan assets at end of year | | 1,102.9 | 914.4 | 867.2 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | | |
Funded status | | (324.9) | (230.8) | |
Current liability, included in accrued liabilities | | 2.8 | 1.9 | |
Noncurrent liability | | 322.1 | 228.9 | |
Net pension liability | | 324.9 | 230.8 | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net gains and losses | | (378.1) | (368) | |
Net actuarial gains (losses) arising during the year | | (59.4) | (53) | |
Reclassification adjustment for amortization of prior actuarial losses included in net income (loss) | | 36.1 | 45.2 | |
Foreign currency exchange effects | | (2.5) | (2.3) | |
End of year - net gains and losses | | (403.9) | (378.1) | (368) |
Benefit plan prior service cost recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net prior service (cost) credit | | (0.5) | (1.2) | |
Prior service credit (cost) from plan amendments during the year | | (0.3) | 0.6 | |
Reclassification adjustment for amortization of prior service cost included in net income (loss) | | 0 | 0.1 | |
Foreign currency exchange effects | | 0.2 | 0 | |
End of year - net prior service (cost) credit | | (0.6) | (0.5) | (1.2) |
Retirement benefits other than pension | | | | |
Changes in the benefit obligation [Roll Forward] | | | | |
Benefit obligation at beginning of year | | 536.7 | 555.6 | |
Service cost | | 0.1 | 0.2 | 0.2 |
Interest cost | | 16.5 | 21.1 | 20.3 |
Plan amendments | | 0 | (0.3) | |
Acquisitions | | 0 | 0.9 | |
Curtailment | | 0 | (0.2) | |
Benefits paid | | (33.1) | (37.8) | |
Actuarial losses | | 40.3 | (2.6) | |
Foreign currency exchange effects | | (2.5) | (0.2) | |
Benefit obligation at end of year | | 558 | 536.7 | 555.6 |
Changes in plan assets [Roll Forward] | | | | |
Fair value of plan assets at beginning of year | | 177.9 | 181.7 | |
Return on assets – actual | | 14.1 | 25.9 | |
Employer contributions | | 7.4 | 8.5 | |
Net transfers to (from) plan assets | | 1.7 | (0.4) | |
Benefits paid | | (33.1) | (37.8) | |
Fair value of plan assets at end of year | | 168 | 177.9 | 181.7 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | | |
Funded status | | (390) | (358.8) | |
Current liability, included in accrued liabilities | | 10.3 | 11 | |
Noncurrent liability | | 379.7 | 347.8 | |
Net pension liability | | 390 | 358.8 | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net gains and losses | | (297.3) | (333.8) | |
Net actuarial gains (losses) arising during the year | | (39.2) | 15.2 | |
Reclassification adjustment for amortization of prior actuarial losses included in net income (loss) | | 24.8 | 21.2 | |
Foreign currency exchange effects | | 1.3 | 0.1 | |
End of year - net gains and losses | | (310.4) | (297.3) | (333.8) |
Benefit plan prior service cost recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net prior service (cost) credit | | 29.4 | 34.2 | |
Prior service credit (cost) from plan amendments during the year | | 0 | 0.3 | |
Reclassification adjustment for amortization of prior service cost included in net income (loss) | | (5) | (5.1) | |
Foreign currency exchange effects | | (0.2) | 0 | |
End of year - net prior service (cost) credit | | 24.2 | 29.4 | 34.2 |
U.S. Plans | | | | |
Changes in the benefit obligation [Roll Forward] | | | | |
Benefit obligation at beginning of year | | 826.8 | 801.9 | |
Service cost | | 0 | 0 | 0 |
Interest cost | | 26.7 | 34.1 | 31.9 |
Participant contributions | | 0 | 0 | |
Plan amendments | | 0 | 0 | |
Plan combinations | | 0 | 0 | |
Settlements | | 0 | (53.6) | |
Benefits paid | | (44) | (49.1) | |
Actuarial losses | | 98.5 | 93.5 | |
Foreign currency exchange effects | | 0 | 0 | |
Benefit obligation at end of year | | 908 | 826.8 | 801.9 |
Changes in plan assets [Roll Forward] | | | | |
Fair value of plan assets at beginning of year | | 699.3 | 686.6 | |
Return on assets – actual | | 91.2 | 114.1 | |
Participant contributions | | 0 | 0 | |
Plan combinations | | 0 | 0 | |
Employer contributions | | 0.6 | 0.7 | |
Settlements | | 0 | (53) | |
Benefits paid | | (44) | (49.1) | |
Foreign currency exchange effects | | 0 | 0 | |
Fair value of plan assets at end of year | | 747.1 | 699.3 | 686.6 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | | |
Funded status | | (160.9) | (127.5) | |
Current liability, included in accrued liabilities | | 0.6 | 0.6 | |
Noncurrent liability | | 160.3 | 126.9 | |
Net pension liability | | 160.9 | 127.5 | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net gains and losses | | (296.6) | (306) | |
Net actuarial gains (losses) arising during the year | | (53.5) | (29.5) | |
Reclassification adjustment for amortization of prior actuarial losses included in net income (loss) | | 28.6 | 38.9 | |
Foreign currency exchange effects | | 0 | 0 | |
End of year - net gains and losses | | (321.5) | (296.6) | (306) |
Benefit plan prior service cost recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net prior service (cost) credit | | 0 | 0 | |
Prior service credit (cost) from plan amendments during the year | | 0 | 0 | |
Reclassification adjustment for amortization of prior service cost included in net income (loss) | | 0 | 0 | |
Foreign currency exchange effects | | 0 | 0 | |
End of year - net prior service (cost) credit | | 0 | 0 | 0 |
U.S. Plans | Actuarial Gains (Losses) - Change in Discount Rate | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | (93) | | |
U.S. Plans | Actuarial Gains (Losses) - Change in Discount Rate | ASU 2017-07 | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | (96) | |
U.S. Plans | Actuarial Gains (Losses) - Change in Census Data | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | (5) | | |
U.S. Plans | Actuarial Gains (Losses) - Asset Return Different from Expected | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | 45 | | |
U.S. Plans | Actuarial Gains (Losses) - Asset Return Different from Expected | ASU 2017-07 | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | 63 | |
U.S. Plans | Actuarial Gains (Losses) - Change of Mortality Tables | ASU 2017-07 | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | 5 | |
U.S. Plans | Total | | | | |
Changes in the benefit obligation [Roll Forward] | | | | |
Settlements | $ (54) | | | |
Non-U.S. Plans | | | | |
Changes in the benefit obligation [Roll Forward] | | | | |
Benefit obligation at beginning of year | | 318.4 | 264.2 | |
Service cost | | 9.7 | 9.9 | 10.5 |
Interest cost | | 11.6 | 10.4 | 11.8 |
Participant contributions | | 0.7 | 0.1 | |
Plan amendments | | 0.3 | (0.6) | |
Plan combinations | | 1 | 1.4 | |
Acquisitions | | 132.5 | | |
Curtailment | | (1.5) | (0.8) | |
Settlements | | (0.7) | (0.9) | |
Benefits paid | | (21.6) | (18.2) | |
Actuarial losses | | 42.9 | 43.2 | |
Foreign currency exchange effects | | 26.5 | 9.7 | |
Benefit obligation at end of year | | 519.8 | 318.4 | 264.2 |
Changes in plan assets [Roll Forward] | | | | |
Fair value of plan assets at beginning of year | | 215.1 | 180.6 | |
Return on assets – actual | | 49.1 | 29.2 | |
Participant contributions | | 0.7 | 0.1 | |
Plan combinations | | 1 | 1.4 | |
Employer contributions | | 14.2 | 13.9 | |
Acquisitions | | 80.3 | | |
Settlements | | (0.7) | (0.9) | |
Benefits paid | | (21.6) | (18.2) | |
Foreign currency exchange effects | | 17.7 | 9 | |
Fair value of plan assets at end of year | | 355.8 | 215.1 | 180.6 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | | |
Funded status | | (164) | (103.3) | |
Current liability, included in accrued liabilities | | 2.2 | 1.3 | |
Noncurrent liability | | 161.8 | 102 | |
Net pension liability | | 164 | 103.3 | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net gains and losses | | (81.5) | (62) | |
Net actuarial gains (losses) arising during the year | | (5.9) | (23.5) | |
Reclassification adjustment for amortization of prior actuarial losses included in net income (loss) | | 7.5 | 6.3 | |
Foreign currency exchange effects | | (2.5) | (2.3) | |
End of year - net gains and losses | | (82.4) | (81.5) | (62) |
Benefit plan prior service cost recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net prior service (cost) credit | | (0.5) | (1.2) | |
Prior service credit (cost) from plan amendments during the year | | (0.3) | 0.6 | |
Reclassification adjustment for amortization of prior service cost included in net income (loss) | | 0 | 0.1 | |
Foreign currency exchange effects | | 0.2 | 0 | |
End of year - net prior service (cost) credit | | (0.6) | (0.5) | (1.2) |
Non-U.S. Plans | Actuarial Gains (Losses) - Change in Discount Rate | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | (45) | (37) | |
Non-U.S. Plans | Actuarial Gains (Losses) - Asset Return Different from Expected | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | 37 | 19 | |
UMWA Plans | | | | |
Changes in the benefit obligation [Roll Forward] | | | | |
Benefit obligation at beginning of year | | 424.6 | 479.1 | |
Service cost | | 0 | 0 | 0 |
Interest cost | | 12.7 | 17.3 | 17.1 |
Plan amendments | | 0 | 0 | |
Curtailment | | 0 | 0 | |
Benefits paid | | (25.7) | (29.3) | |
Actuarial losses | | 28.5 | (42.5) | |
Foreign currency exchange effects | | 0 | 0 | |
Benefit obligation at end of year | | 440.1 | 424.6 | 479.1 |
Changes in plan assets [Roll Forward] | | | | |
Fair value of plan assets at beginning of year | | 177.9 | 181.7 | |
Return on assets – actual | | 14.1 | 25.9 | |
Net transfers to (from) plan assets | | 1.7 | (0.4) | |
Benefits paid | | (25.7) | (29.3) | |
Fair value of plan assets at end of year | | 168 | 177.9 | 181.7 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | | |
Funded status | | (272.1) | (246.7) | |
Current liability, included in accrued liabilities | | 0 | 0 | |
Noncurrent liability | | 272.1 | 246.7 | |
Net pension liability | | 272.1 | 246.7 | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net gains and losses | | (219.2) | (290.9) | |
Net actuarial gains (losses) arising during the year | | (27.4) | | |
Reclassification adjustment for amortization of prior actuarial losses included in net income (loss) | | 16.5 | 16.6 | |
Foreign currency exchange effects | | 0 | 0 | |
End of year - net gains and losses | | (230.1) | (219.2) | (290.9) |
Benefit plan prior service cost recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net prior service (cost) credit | | 28 | 32.7 | |
Prior service credit (cost) from plan amendments during the year | | 0 | 0 | |
Reclassification adjustment for amortization of prior service cost included in net income (loss) | | (4.7) | (4.7) | |
Foreign currency exchange effects | | 0 | 0 | |
End of year - net prior service (cost) credit | | 23.3 | 28 | 32.7 |
UMWA Plans | ASU 2017-07 | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | 55.1 | |
UMWA Plans | Actuarial Gains (Losses) - Change in Discount Rate | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | (37) | | |
UMWA Plans | Actuarial Gains (Losses) - Change in Discount Rate | ASU 2017-07 | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | (50) | |
UMWA Plans | Actuarial Gains (Losses) - Change in Census Data | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | 4 | |
UMWA Plans | Actuarial Gains (Losses) - Asset Return Different from Expected | ASU 2017-07 | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | 13 | |
UMWA Plans | Actuarial Gains (Losses) - Change of Mortality Tables | ASU 2017-07 | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | 6 | |
UMWA Plans | Actuarial Gains (Losses) - Change in Claims Experience | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | 10 | 53 | |
UMWA Plans | Actuarial Gains (Losses) - Excise Tax Update | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | 29 | |
Black Lung and Other Plans | | | | |
Changes in the benefit obligation [Roll Forward] | | | | |
Benefit obligation at beginning of year | | 112.1 | 76.5 | |
Service cost | | 0.1 | 0.2 | 0.2 |
Interest cost | | 3.8 | 3.8 | 3.2 |
Plan amendments | | 0 | (0.3) | |
Acquisitions | | 0 | 0.9 | |
Curtailment | | 0 | (0.2) | |
Benefits paid | | (7.4) | (8.5) | |
Actuarial losses | | 11.8 | 39.9 | |
Foreign currency exchange effects | | (2.5) | (0.2) | |
Benefit obligation at end of year | | 117.9 | 112.1 | 76.5 |
Changes in plan assets [Roll Forward] | | | | |
Fair value of plan assets at beginning of year | | 0 | 0 | |
Return on assets – actual | | 0 | 0 | |
Employer contributions | | 7.4 | 8.5 | |
Benefits paid | | (7.4) | (8.5) | |
Fair value of plan assets at end of year | | 0 | 0 | 0 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | | |
Funded status | | (117.9) | (112.1) | |
Current liability, included in accrued liabilities | | 10.3 | 11 | |
Noncurrent liability | | 107.6 | 101.1 | |
Net pension liability | | 117.9 | 112.1 | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net gains and losses | | (78.1) | (42.9) | |
Net actuarial gains (losses) arising during the year | | (11.8) | | |
Reclassification adjustment for amortization of prior actuarial losses included in net income (loss) | | 8.3 | 4.6 | |
Foreign currency exchange effects | | 1.3 | 0.1 | |
End of year - net gains and losses | | (80.3) | (78.1) | (42.9) |
Benefit plan prior service cost recognized in accumulated other comprehensive income (loss): | | | | |
Beginning of year - net prior service (cost) credit | | 1.4 | 1.5 | |
Prior service credit (cost) from plan amendments during the year | | 0 | 0.3 | |
Reclassification adjustment for amortization of prior service cost included in net income (loss) | | (0.3) | (0.4) | |
Foreign currency exchange effects | | (0.2) | 0 | |
End of year - net prior service (cost) credit | | 0.9 | 1.4 | $ 1.5 |
Black Lung and Other Plans | ASU 2017-07 | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | (39.9) | |
Black Lung and Other Plans | Actuarial Gains (Losses) - Change in Discount Rate | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | (8) | | |
Black Lung and Other Plans | Actuarial Gains (Losses) - Change in Discount Rate | ASU 2017-07 | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | (5) | |
Black Lung and Other Plans | Actuarial Gains (Losses) - Change in Census Data | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | (5) | | |
Black Lung and Other Plans | Actuarial Gains (Losses) - Change in Census Data | ASU 2017-07 | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | (8) | |
Black Lung and Other Plans | Actuarial Gains (Losses) - Change of Mortality Tables | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | | 3 | |
Black Lung and Other Plans | Actuarial Gains (Losses) - Claims Assumptions Updates | | | | |
Benefit plan net actuarial losses recognized in accumulated other comprehensive income (loss): | | | | |
Net actuarial gains (losses) arising during the year | | $ 3 | $ (27) | |