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Employee Benefits - Additional Information (Details) - USD ($)		9 Months Ended	12 Months Ended
	Sep. 07, 2018	Sep. 30, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Service costs included in net periodic pension expense		$ 0
Expected long-term rate of return on plan assets		7.50%
Pension contribution	$ 20,400,000
Return to provision discrete tax benefit due to decrease in federal statutory tax rate			$ 2,900,000

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Tax Cuts And Jobs Act Of 2017, Income Tax Expense (Benefit)

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Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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