Geographic Area Data (Summary of Geographic Area Data) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Mar. 31, 2024
Quarter ended:
Total revenues	$ 1,658,108	$ 1,649,860	$ 3,206,598	$ 3,190,168
Depreciation and amortization, net of (gains) losses on disposals	234,700	162,663	458,995	309,543
Interest expense	71,498	63,943	138,716	124,541
Pretax earnings	246,217	358,048	502,609	696,743
Income tax expense	59,419	84,540	120,394	166,397
Identifiable assets	20,126,551	19,021,450	20,126,551	19,021,450	$ 19,058,758
United States [Member]
Quarter ended:
Total revenues	1,565,478	1,559,205	3,033,171	3,020,489
Depreciation and amortization, net of (gains) losses on disposals	226,600	161,085	446,012	309,398
Interest expense	70,924	63,182	137,673	123,128
Pretax earnings	236,601	348,442	483,919	675,514
Income tax expense	56,712	82,035	115,089	160,630
Identifiable assets	19,238,854	18,279,234	19,238,854	18,279,234
Canada [Member]
Quarter ended:
Total revenues	92,630	90,655	173,427	169,679
Depreciation and amortization, net of (gains) losses on disposals	8,100	1,578	12,983	145
Interest expense	574	761	1,043	1,413
Pretax earnings	9,616	9,606	18,690	21,229
Income tax expense	2,707	2,505	5,305	5,767
Identifiable assets	$ 887,697	$ 742,216	$ 887,697	$ 742,216