Employee Benefit Plans - Weighted Average Discount Rate Used to Determine the Net Periodic Postretirement Benefit Costs (Details) - Other Postretirement Benefit Plan	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Net periodic postretirement benefit costs	2.92%	3.90%
Accumulated postretirement benefit obligations	2.11%	2.92%