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Pension and Other Postretirement Benefits - Company matching contribution to defined contribution 401(K) plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Age requirement for future accruals	50 years
Company matching contribution to defined contribution (401(k)) plans	$ 4.9	$ 4.9	$ 4.4

X

- Definition

Defined Contribution Plan, Age Requirement for Future Accruals

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No definition available.

+ Details

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- References

No definition available.

+ Details

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- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

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No definition available.

+ Details

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