Employee Benefit Plans and Other Postretirement Benefits - Additional Information (Details) - Pension Plans - Qualified Plan - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Contributions [Abstract]
Contributions to pension plan	$ 3,900,000	$ 1,000,000.0	$ 4,600,000	$ 3,200,000
Minimum
Pension Contributions [Abstract]
Expected contributions to pension plan	$ 15,800,000		$ 15,800,000