Geographic Area Data (Summary of Geographic Area Data) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Mar. 31, 2023
Quarter ended:
Total revenues	$ 1,339,514	$ 1,375,336	$ 4,529,682	$ 4,676,040
Depreciation and amortization, net of (gains) losses on disposals	180,387	121,704	489,930	371,641
Interest expense	67,450	59,041	191,991	166,033
Pretax earnings	129,773	260,616	826,516	1,167,505
Income tax expense	30,549	61,764	196,946	280,442
Identifiable assets	19,002,576	18,090,124	19,002,576	18,090,124	$ 18,100,734
United States [Member]
Quarter ended:
Total revenues	1,273,821	1,311,117	4,294,310	4,431,570
Depreciation and amortization, net of (gains) losses on disposals	176,864	119,864	486,262	365,585
Interest expense	66,772	58,367	189,900	163,792
Pretax earnings	125,531	253,386	801,045	1,129,487
Income tax expense	29,172	59,774	189,802	270,641
Identifiable assets	18,225,204	17,447,581	18,225,204	17,447,581
Canada [Member]
Quarter ended:
Total revenues	65,693	64,219	235,372	244,470
Depreciation and amortization, net of (gains) losses on disposals	3,523	1,840	3,668	6,056
Interest expense	678	674	2,091	2,241
Pretax earnings	4,242	7,230	25,471	38,018
Income tax expense	1,377	1,990	7,144	9,801
Identifiable assets	$ 777,372	$ 642,543	$ 777,372	$ 642,543