Pension and Other Post Retirement Benefits (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) uSDollarPerHour	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
IAM Level of Contribution per hour until June 2019 | uSDollarPerHour	1.75
Amounts recognized in balance sheet
Noncurrent assets	$ 455,900,000	$ 449,100,000
Noncurrent liabilities	(440,200,000)	(35,700,000)
Information for pension plans with benefit obligations in excess of plan assets:
Multiemployer Plan, Employer Contribution, Cost	$ 30,100,000	$ 40,700,000	$ 35,000,000.0
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	Yes
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Red	Red
UNITED STATES
Change in fair value of plan assets:
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	$ 0	$ 0
Defined Benefit Plan, Plan Assets, Payment for Settlement	$ (175,500,000)	(49,900,000)
UNITED STATES | Minimum [Member] | Defined Benefit Plan, Equity Securities
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	20.00%
UNITED STATES | Minimum [Member] | Defined Benefit Plan, Debt Security
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	50.00%
UNITED STATES | Minimum [Member] | Defined Benefit Plan, Real Estate
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
UNITED STATES | Maximum [Member] | Defined Benefit Plan, Equity Securities
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	50.00%
UNITED STATES | Maximum [Member] | Defined Benefit Plan, Debt Security
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	80.00%
UNITED STATES | Maximum [Member] | Defined Benefit Plan, Real Estate
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	7.00%
Belfast
Change in fair value of plan assets:
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	$ 100,000	0
Belfast | Defined Benefit Plan, Equity Securities
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	3200.00%
Belfast | Defined Benefit Plan, Debt Security
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	3600.00%
Belfast | Other Debt Obligations
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	1500.00%
Belfast | Defined Benefit Plan, Real Assets
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	1500.00%
Belfast | Money Market Fund [Member]
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	200.00%
UNITED KINGDOM | Minimum [Member] | Defined Benefit Plan, Equity Securities
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	12.00%
UNITED KINGDOM | Minimum [Member] | Defined Benefit Plan, Debt Security
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	80.00%
UNITED KINGDOM | Minimum [Member] | Defined Benefit Plan, Real Estate
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	6.00%
UNITED KINGDOM | Maximum [Member] | Defined Benefit Plan, Equity Securities
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	14.00%
UNITED KINGDOM | Maximum [Member] | Defined Benefit Plan, Debt Security
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	80.00%
UNITED KINGDOM | Maximum [Member] | Defined Benefit Plan, Real Estate
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	8.00%
Other Benefits [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	$ 0	0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment	2,300,000
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	41,800,000	40,300,000
Service cost	800,000	900,000
Interest cost	1,000,000.0	1,200,000
Actuarial loss (gain)	1,800,000	(1,800,000)
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	12,000,000.0	3,900,000
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	0	0
Defined Benefit Plan, Benefit Obligation, Benefits Paid	7,800,000	7,200,000
Projected benefit obligation at the end of the period	49,500,000	41,800,000	40,300,000
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	$ 1,200,000	$ 900,000
Total recognized in other net periodic benefit and OCI (income) loss
Discount rate	1.26%	2.55%
Medical Assumptions:
Trend assumed for the year	5.56%	5.90%
Ultimate trend rate	4.50%	4.50%
Year that ultimate trend rate is reached	2038	2038
Change in fair value of plan assets:
Beginning balance	$ 0	$ 0
Company contributions	6,600,000	6,300,000
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	1,200,000	900,000
Defined Benefit Plan, Plan Assets, Benefits Paid	7,800,000	7,200,000
Defined Benefit Plan, Plan Assets, Administration Expense	0	0
Ending balance	0	0	0
Defined Benefit Plan, Plan Assets, Payment for Settlement	0	0
Reconciliation of funded status to net amounts recognized:
Funded status (deficit)	(49,500,000)	(41,800,000)
Net amounts recognized	(49,500,000)	(41,800,000)
Amounts recognized in balance sheet
Noncurrent assets	0	0
Current liabilities	(10,300,000)	(7,300,000)
Noncurrent liabilities	(39,200,000)	(34,500,000)
Net amounts recognized	(49,500,000)	(41,800,000)
Amounts not yet reflected in net periodic benefit cost and included in AOCI:
Accumulated gain (loss)	19,300,000	22,600,000
Accumulated other comprehensive income (AOCI)	19,300,000	22,600,000
Cumulative employer contributions in excess of net periodic benefit cost	(68,800,000)	(64,400,000)
Net amount recognized in the balance sheet	(49,500,000)	(41,800,000)
Information for pension plans with benefit obligations in excess of plan assets:
Projected benefit obligation	49,500,000	41,800,000
Accumulated benefit obligation	0	0
Other Benefits [Member] | Belfast
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	0	0
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	0	0
Service cost	0	0
Interest cost	0	0
Actuarial loss (gain)	0	0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	0	0
Defined Benefit Plan, Benefit Obligation, Business Combination	700,000	0
Exchange rate changes	100,000	0
Projected benefit obligation at the end of the period	800,000	0	0
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	$ 0	$ 0
Total recognized in other net periodic benefit and OCI (income) loss
Discount rate	1.45%	0.00%
Medical Assumptions:
Trend assumed for the year	5.50%	0.00%
Ultimate trend rate	5.50%	0.00%
Change in fair value of plan assets:
Beginning balance	$ 0	$ 0
Company contributions	0	0
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	0	0
Defined Benefit Plan, Plan Assets, Benefits Paid	0	0
Defined Benefit Plan, Plan Assets, Administration Expense	0	0
Ending balance	0	0	0
Defined Benefit Plan, Plan Assets, Business Combination	0	0
Reconciliation of funded status to net amounts recognized:
Funded status (deficit)	(800,000)	0
Net amounts recognized	(800,000)	0
Amounts recognized in balance sheet
Noncurrent liabilities	(800,000)	0
Net amounts recognized	(800,000)	0
Amounts not yet reflected in net periodic benefit cost and included in AOCI:
Accumulated gain (loss)	(800,000)	0
Accumulated other comprehensive income (AOCI)	(800,000)	0
Cumulative employer contributions in excess of net periodic benefit cost	0	0
Net amount recognized in the balance sheet	(800,000)	0
Information for pension plans with benefit obligations in excess of plan assets:
Projected benefit obligation	0	0
Accumulated benefit obligation	0	0
Pension Plan [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	218,400,000	299,700,000
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment	33,900,000	0
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	1,096,600,000	997,000,000.0
Service cost	0	0
Interest cost	24,400,000	36,500,000
Actuarial loss (gain)	(124,800,000)	(141,100,000)
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	31,000,000.0	5,200,000
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	(175,500,000)	(49,900,000)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	36,100,000	33,300,000
Projected benefit obligation at the end of the period	1,099,100,000	1,096,600,000	997,000,000.0
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	$ 0	$ 0
Total recognized in other net periodic benefit and OCI (income) loss
Discount rate	2.31%	3.19%
Change in fair value of plan assets:
Beginning balance	$ 1,519,500,000	$ 1,302,800,000
Company contributions	100,000	100,000
Defined Benefit Plan, Plan Assets, Benefits Paid	36,200,000	33,200,000
Defined Benefit Plan, Plan Assets, Administration Expense	0	0
Ending balance	1,526,300,000	1,519,500,000	1,302,800,000
Reconciliation of funded status to net amounts recognized:
Funded status (deficit)	427,300,000	422,900,000
Net amounts recognized	427,300,000	422,900,000
Amounts recognized in balance sheet
Noncurrent assets	428,700,000	424,200,000
Current liabilities	(100,000)	(100,000)
Noncurrent liabilities	(1,300,000)	(1,200,000)
Net amounts recognized	427,300,000	422,900,000
Amounts not yet reflected in net periodic benefit cost and included in AOCI:
Accumulated gain (loss)	(6,500,000)	(46,000,000.0)
Accumulated other comprehensive income (AOCI)	(6,500,000)	(46,000,000.0)
Cumulative employer contributions in excess of net periodic benefit cost	433,800,000	468,900,000
Net amount recognized in the balance sheet	427,300,000	422,900,000
Information for pension plans with benefit obligations in excess of plan assets:
Projected benefit obligation	1,400,000	1,300,000
Accumulated benefit obligation	1,400,000	1,300,000
Pension Plan [Member] | Belfast
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	125,900,000	0
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	0	0
Service cost	6,300,000	0
Interest cost	6,000,000.0	0
Actuarial loss (gain)	(183,900,000)	0
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	0	0
Defined Benefit Plan, Benefit Obligation, Business Combination	2,311,800,000	0
Exchange rate changes	161,600,000	0
Projected benefit obligation at the end of the period	2,661,400,000	0	0
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	$ 0	$ 0
Total recognized in other net periodic benefit and OCI (income) loss
Discount rate	1.45%	0.00%
Salary increases	2.90%
Change in fair value of plan assets:
Beginning balance	$ 0	$ 0
Company contributions	3,800,000	0
Defined Benefit Plan, Plan Assets, Benefits Paid	8,200,000	0
Defined Benefit Plan, Plan Assets, Administration Expense	137,400,000	0
Ending balance	2,262,700,000	0	0
Defined Benefit Plan, Plan Assets, Business Combination	2,003,700,000	0
Reconciliation of funded status to net amounts recognized:
Funded status (deficit)	(398,800,000)	0
Net amounts recognized	(398,800,000)	0
Amounts recognized in balance sheet
Noncurrent liabilities	(398,800,000)	0
Net amounts recognized	(398,800,000)	0
Amounts not yet reflected in net periodic benefit cost and included in AOCI:
Accumulated gain (loss)	(404,700,000)	0
Accumulated other comprehensive income (AOCI)	(404,700,000)	0
Cumulative employer contributions in excess of net periodic benefit cost	5,900,000	0
Net amount recognized in the balance sheet	(398,800,000)	0
Information for pension plans with benefit obligations in excess of plan assets:
Projected benefit obligation	2,661,500,000	0
Accumulated benefit obligation	2,594,500,000	0
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Fair value of assets	2,262,700,000
Pension Plan [Member] | UNITED KINGDOM
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	15,100,000	11,100,000
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment	(5,900,000)	(2,100,000)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	66,700,000	59,900,000
Service cost	900,000	900,000
Interest cost	1,200,000	1,600,000
Actuarial loss (gain)	(12,200,000)	(5,500,000)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	800,000	800,000
Expense paid	(900,000)	(900,000)
Exchange rate changes	2,500,000	2,600,000
Projected benefit obligation at the end of the period	$ 75,900,000	$ 66,700,000	59,900,000
Total recognized in other net periodic benefit and OCI (income) loss
Discount rate	1.45%	2.10%
Salary increases	3.10%	3.15%
Change in fair value of plan assets:
Beginning balance	$ 91,600,000	$ 79,600,000
Company contributions	1,700,000	1,700,000
Expense paid	(900,000)	(900,000)
Exchange rate changes	3,300,000	3,500,000
Defined Benefit Plan, Plan Assets, Benefits Paid	800,000	800,000
Defined Benefit Plan, Plan Assets, Administration Expense	900,000	900,000
Ending balance	103,100,000	91,600,000	79,600,000
Defined Benefit Plan, Plan Assets, Payment for Settlement	(6,900,000)	(2,600,000)
Reconciliation of funded status to net amounts recognized:
Funded status (deficit)	27,200,000	24,900,000
Net amounts recognized	27,200,000	24,900,000
Amounts recognized in balance sheet
Noncurrent assets	27,200,000	24,900,000
Net amounts recognized	27,200,000	24,900,000
Amounts not yet reflected in net periodic benefit cost and included in AOCI:
Accumulated gain (loss)	5,800,000	5,900,000
Accumulated other comprehensive income (AOCI)	5,800,000	5,900,000
Prepaid pension cost	21,400,000	19,000,000.0
Net amount recognized in the balance sheet	27,200,000	24,900,000
Annual Expense [Member] | Other Benefits [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0	0
Defined Benefit Plan, Amortization of Gain (Loss)	(1,700,000)	(2,200,000)	(2,300,000)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	12,000,000.0	(7,800,000)	200,000
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment	(200,000)	0	0
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	800,000	900,000	1,100,000
Interest cost	1,000,000.0	1,200,000	1,100,000
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	$ (12,000,000.0)	$ (3,900,000)	$ 0
Total recognized in other net periodic benefit and OCI (income) loss
Discount rate	2.55%	3.74%	3.03%
Medical Assumptions:
Trend assumed for the year	5.90%	6.24%	6.59%
Ultimate trend rate	4.50%	4.50%	4.50%
Year that ultimate trend rate is reached	2038	2038	2038
Amounts not yet reflected in net periodic benefit cost and included in AOCI:
Accumulated gain (loss)	$ 1,000,000.0	$ 4,900,000	$ 800,000
Accumulated other comprehensive income (AOCI)	1,000,000.0	4,900,000	800,000
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	11,000,000.0	2,900,000	(1,000,000.0)
Annual Expense [Member] | Pension Plan [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	(9,800,000)	(3,400,000)	0
Defined Benefit Plan, Amortization of Gain (Loss)	200,000	500,000	0
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	(4,300,000)	117,000,000.0	(20,100,000)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment	33,900,000	0	0
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	0	0	0
Interest cost	24,400,000	36,500,000	34,700,000
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	$ (31,000,000.0)	$ (5,200,000)	$ 0
Total recognized in other net periodic benefit and OCI (income) loss
Discount rate	3.19%	4.21%	3.59%
Amounts not yet reflected in net periodic benefit cost and included in AOCI:
Accumulated gain (loss)	$ (39,400,000)	$ (95,900,000)	$ 52,300,000
Accumulated other comprehensive income (AOCI)	(39,400,000)	(95,900,000)	52,300,000
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(64,200,000)	(66,700,000)	(66,900,000)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 35,100,000	$ (21,100,000)	$ (32,200,000)
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	4.50%	5.00%	4.80%
Annual Expense [Member] | Pension Plan [Member] | Belfast
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	$ 94,800,000	$ 0	$ 0
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	6,300,000	0	0
Interest cost	$ 5,900,000	0	0
Total recognized in other net periodic benefit and OCI (income) loss
Discount rate	1.75%
Salary increases	2.75%
Amounts not yet reflected in net periodic benefit cost and included in AOCI:
Accumulated gain (loss)	$ 96,600,000	0	0
Accumulated other comprehensive income (AOCI)	96,600,000	0	0
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(14,000,000.0)	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ (1,800,000)	0	0
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	4.20%
Annual Expense [Member] | Pension Plan [Member] | UNITED KINGDOM
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ 400,000	200,000	400,000
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	(900,000)	3,200,000	700,000
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	900,000	900,000	1,300,000
Interest cost	$ 1,200,000	$ 1,700,000	$ 1,700,000
Total recognized in other net periodic benefit and OCI (income) loss
Discount rate	2.10%	3.00%	2.60%
Salary increases	3.15%	3.40%	3.35%
Amounts not yet reflected in net periodic benefit cost and included in AOCI:
Accumulated gain (loss)	$ (900,000)	$ (3,200,000)	$ (500,000)
Accumulated other comprehensive income (AOCI)	(900,000)	(3,200,000)	(500,000)
Information for pension plans with benefit obligations in excess of plan assets:
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(1,700,000)	(2,400,000)	(2,800,000)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 0	$ 0	$ (200,000)
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	2.00%	3.10%	3.10%