Industry Segment and Geographic Area Data (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Mar. 31, 2022
Quarter ended:
Total revenues	$ 1,702,864	$ 1,664,254	$ 3,300,704	$ 3,137,110
Depreciation and amortization, net of (gains) losses on disposals	126,162	143,021	249,937	269,131
Interest expense	57,193	39,545	106,992	78,723
Pretax earnings (loss)	463,639	538,876	904,695	993,626
Income tax expense	111,624	128,978	218,678	238,553
Identifiable assets	18,143,343	16,337,228	18,143,343	16,337,228	$ 17,299,581
United States [Member]
Quarter ended:
Total revenues	1,610,067	1,576,830	3,120,453	2,973,191
Depreciation and amortization, net of (gains) losses on disposals	124,735	141,956	245,721	269,606
Interest expense	56,477	38,588	105,425	76,716
Pretax earnings (loss)	446,369	521,658	873,907	959,607
Income tax expense	107,254	124,620	210,867	229,922
Identifiable assets	17,515,009	15,849,380	17,515,009	15,849,380
Canada [Member]
Quarter ended:
Total revenues	92,797	87,424	180,251	163,919
Depreciation and amortization, net of (gains) losses on disposals	1,427	1,065	4,216	(475)
Interest expense	716	957	1,567	2,007
Pretax earnings (loss)	17,270	17,218	30,788	34,019
Income tax expense	4,370	4,358	7,811	8,631
Identifiable assets	$ 628,334	$ 487,848	$ 628,334	$ 487,848