Retirement Benefits - Summary of Basis Used to Measure Defined Benefit Plans Assets at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	$ 142,136	$ 132,717
U.S. Large Cap
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	3,710	4,734
U.S. Small / Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	444	455
International, Equity
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	10,427	10,845
U.S. Intermediate
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	14,263	640
U.S. Long Term
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	51,891	83,628
U.S. High Yield
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	296	1,346
International, Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	8,448	7,516
Other Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	20,665	19,438
Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	28,469	1,094
Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	3,523	3,021
Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	36,205	10,805
Level 1 | U.S. Large Cap
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	3,710	4,734
Level 1 | U.S. Small / Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 1 | International, Equity
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	4,412	5,258
Level 1 | U.S. Intermediate
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 1 | U.S. Long Term
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 1 | U.S. High Yield
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 1 | International, Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	257	296
Level 1 | Other Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 1 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	27,826	517
Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	85,266	102,474
Level 2 | U.S. Large Cap
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 2 | U.S. Small / Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	444	455
Level 2 | International, Equity
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	6,015	5,587
Level 2 | U.S. Intermediate
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	14,263	640
Level 2 | U.S. Long Term
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	51,891	83,628
Level 2 | U.S. High Yield
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	296	1,346
Level 2 | International, Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	8,191	7,220
Level 2 | Other Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 2 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	643	577
Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	3,523	3,021
Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	20,665	19,438
Level 3 | U.S. Large Cap
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 3 | U.S. Small / Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 3 | International, Equity
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 3 | U.S. Intermediate
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 3 | U.S. Long Term
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 3 | U.S. High Yield
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 3 | International, Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 3 | Other Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	20,665	19,438
Level 3 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Level 3 | Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	$ 0	$ 0