Employee Benefit Plans (Details) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2019
Retirement Benefits [Abstract]
Employer matching contribution, percent of match			6.00%
Employees’ capital accumulation plan, total expense recognized	$ 36,700,000	$ 32,300,000	$ 109,800,000	$ 98,500,000
Employees’ capital accumulation plan, company-paid contributions	20,400,000	17,300,000	62,400,000	51,700,000
Defined Benefit Plan Disclosure [Line Items]
Long-term disability obligation	11,600,000		$ 11,600,000		$ 11,600,000
Maximum eligible deferral of compensation, percentage			100.00%
Deferred compensation plan, assets	7,000,000.0		$ 7,000,000.0		3,200,000
Deferred compensation plan, liabilities	7,000,000		7,000,000		3,200,000
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation arrangement with individual, annual cash award granted per year of service, amount			10,000
Officer Medical Plan | Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,238,000	1,488,000	3,716,000	4,464,000
Interest cost	1,214,000	1,283,000	3,644,000	3,847,000
Net actuarial loss	0	527,000	0	1,581,000
Total postretirement medical expense	2,452,000	$ 3,298,000	7,360,000	$ 9,892,000
Defined benefit plan, unfunded status of plan	$ 124,900,000		$ 124,900,000		$ 120,300,000