Industry Segment and Geographic Area Data (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020
Quarter ended:
Total revenues	$ 987,237	$ 1,079,249
Depreciation and amortization, net of (gains) losses on disposals	172,303	145,042
Interest expense	39,521	38,888
Pretax earnings (loss)	114,318	174,714
Income tax expense	26,592	42,292
Identifiable assets	13,712,359	12,474,744	$ 13,438,024
United States [Member]
Quarter ended:
Total revenues	942,803	1,028,574
Depreciation and amortization, net of (gains) losses on disposals	168,526	141,898
Interest expense	38,654	38,220
Pretax earnings (loss)	111,949	170,847
Income tax expense	25,783	41,114
Identifiable assets	13,279,882	12,076,714
Canada [Member]
Quarter ended:
Total revenues	44,434	50,675
Depreciation and amortization, net of (gains) losses on disposals	3,777	3,144
Interest expense	867	668
Pretax earnings (loss)	2,369	3,867
Income tax expense	809	1,178
Identifiable assets	$ 432,477	$ 398,030