Financial Information by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Fiscal year ended:
Total revenues	$ 4,541,985	$ 3,978,868	$ 3,768,707
Depreciation and amortization, net of (gains) losses on disposals	641,504	667,524	582,555
Interest expense	163,502	160,950	142,445
Pretax earnings	796,658	378,124	477,529
Income tax expense	185,802	(63,924)	106,672
Identifiable assets	14,651,606	13,438,024	11,891,713
United States [Member]
Fiscal year ended:
Total revenues	4,334,083	3,797,849	3,597,285
Depreciation and amortization, net of (gains) losses on disposals	631,344	652,110	575,134
Interest expense	160,429	157,595	139,573
Pretax earnings	773,030	372,687	466,175
Income tax expense	180,845	(65,842)	103,578
Identifiable assets	14,212,978	13,016,942	11,526,876
Canada [Member]
Fiscal year ended:
Total revenues	207,902	181,019	171,422
Depreciation and amortization, net of (gains) losses on disposals	10,160	15,414	7,421
Interest expense	3,073	3,355	2,872
Pretax earnings	23,628	5,437	11,354
Income tax expense	4,957	1,918	3,094
Identifiable assets	$ 438,628	$ 421,082	$ 364,837