Industry Segment and Geographic Area Data (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Quarter ended:
Total revenues	$ 1,649,860	$ 1,702,864	$ 3,190,168	$ 3,300,704
Depreciation and amortization, net of (gains) losses on disposals	162,663	126,162	309,543	249,937
Interest expense	63,943	57,193	124,541	106,992
Pretax earnings (loss)	358,048	461,490	696,743	906,889
Income tax expense	84,540	111,624	166,397	218,678
Identifiable assets	19,021,450	18,143,343	19,021,450	18,143,343	$ 18,100,734
United States [Member]
Quarter ended:
Total revenues	1,559,205	1,610,067	3,020,489	3,120,453
Depreciation and amortization, net of (gains) losses on disposals	161,085	124,735	309,398	245,721
Interest expense	63,182	56,477	123,128	105,425
Pretax earnings (loss)	348,442	444,220	675,514	876,101
Income tax expense	82,035	107,254	160,630	210,867
Identifiable assets	18,279,234	17,515,009	18,279,234	17,515,009
Canada [Member]
Quarter ended:
Total revenues	90,655	92,797	169,679	180,251
Depreciation and amortization, net of (gains) losses on disposals	1,578	1,427	145	4,216
Interest expense	761	716	1,413	1,567
Pretax earnings (loss)	9,606	17,270	21,229	30,788
Income tax expense	2,505	4,370	5,767	7,811
Identifiable assets	$ 742,216	$ 628,334	$ 742,216	$ 628,334