Financial Information by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Fiscal year ended:
Total revenues	$ 3,978,868	$ 3,768,707	$ 3,601,114
Depreciation and amortization, net of (gains) losses on disposals	667,524	582,555	372,347
Pretax earnings	378,124	477,529	637,613
Identifiable assets	13,438,024	11,891,713	10,747,422
United States [Member]
Fiscal year ended:
Total revenues	3,797,849	3,597,285	3,435,821
Depreciation and amortization, net of (gains) losses on disposals	652,110	575,134	363,826
Interest expense	157,595	139,573	123,777
Pretax earnings	372,687	466,175	628,901
Income tax expense	(65,842)	103,578	(155,685)
Identifiable assets	13,016,942	11,526,876	10,425,299
Canada [Member]
Fiscal year ended:
Total revenues	181,019	171,422	165,293
Depreciation and amortization, net of (gains) losses on disposals	15,414	7,421	8,521
Interest expense	3,355	2,872	2,929
Pretax earnings	5,437	11,354	8,712
Income tax expense	1,918	3,094	2,715
Identifiable assets	$ 421,082	$ 364,837	$ 322,123