Employee Benefit Plans - Schedule of Assets by Investment Type (Detail)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Chesapeake Pension Plan
Asset Category
Percentage of assets by investment type	100.00%	100.00%	100.00%
Chesapeake Pension Plan | Investments in equity securities
Asset Category
Percentage of assets by investment type	0.00%	49.00%	53.00%
Chesapeake Pension Plan | Debt securities
Asset Category
Percentage of assets by investment type	92.00%	41.00%	38.00%
Chesapeake Pension Plan | Other
Asset Category
Percentage of assets by investment type	8.00%	10.00%	9.00%
FPU Pension Plan
Asset Category
Percentage of assets by investment type	100.00%	100.00%	100.00%
FPU Pension Plan | Investments in equity securities
Asset Category
Percentage of assets by investment type	53.00%	50.00%	55.00%
FPU Pension Plan | Debt securities
Asset Category
Percentage of assets by investment type	37.00%	41.00%	37.00%
FPU Pension Plan | Other
Asset Category
Percentage of assets by investment type	10.00%	9.00%	8.00%