Industry Segment and Geographic Area Data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2019
Quarter ended:
Total revenues	$ 927,880	$ 919,091	$ 3,157,343	$ 3,043,175
Depreciation and amortization, net of (gains) losses on disposals	178,648	150,127	481,541	421,119
Pretax earnings (loss)	40,329	103,022	420,397	487,879
Identifiable assets	12,994,322	11,645,760	12,994,322	11,645,760	$ 11,891,713
United States [Member]
Quarter ended:
Total revenues	886,731	880,767	3,008,067	2,901,908
Depreciation and amortization, net of (gains) losses on disposals	174,669	147,868	471,535	416,784
Interest expense	39,042	34,051	115,523	102,924
Pretax earnings (loss)	40,606	100,832	411,565	472,302
Income tax expense	9,303	23,828	97,951	113,712
Identifiable assets	12,575,914	11,285,627	12,575,914	11,285,627
Canada [Member]
Quarter ended:
Total revenues	41,149	38,324	149,276	141,267
Depreciation and amortization, net of (gains) losses on disposals	3,979	2,259	10,006	4,335
Interest expense	931	776	2,460	2,187
Pretax earnings (loss)	(277)	2,190	8,832	15,577
Income tax expense	94	559	2,766	4,141
Identifiable assets	$ 418,408	$ 360,133	$ 418,408	$ 360,133