Pension Benefits and Other Postretirement Benefits (Additional Information) (Details)		2 Months Ended		3 Months Ended			6 Months Ended		12 Months Ended
	Oct. 17, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) plan	Jul. 27, 2020 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of qualified noncontributory defined benefit plans | plan									2
Pension assets		$ 12,790,000	$ 12,790,000	$ 4,173,000	$ 12,790,000		$ 4,173,000		$ 12,790,000
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Payment for settlement	$ 123,300,000	$ 1,300,000
Lump sum distributions			$ 38,900,000
Settlement charge				0	$ (53,200,000)
Pension assets				9,700,000			9,700,000
Contributions				0		$ 0	0
Pension Benefits | Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Pension assets										$ 7,400,000
Pension Benefits | Union Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions				$ 0		$ 0	$ 0	$ 0
Pension Benefits | Merged Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions								$ 0