Industry Segment and Geographic Area Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2012
Quarter ended:
Total revenues	$ 578,811	$ 633,089	$ 1,985,544	$ 1,979,235
Depreciation and amortization, net of (gains) losses on disposals	65,790	59,940	186,768	159,412
Interest expense	22,076	22,744	67,680	68,340
Pretax earnings	59,870	2,129	359,467	289,329
Income tax expense	23,024	1,401	132,632	109,367
Identifiable assets	5,219,305	4,634,002	5,219,305	4,634,002	4,654,051
United States
Quarter ended:
Total revenues	545,935	600,609	1,862,680	1,857,795
Depreciation and amortization, net of (gains) losses on disposals	63,801	57,983	180,736	153,536
Interest expense	21,926	22,579	67,226	67,851
Pretax earnings	58,669	(2,567)	340,746	267,811
Income tax expense	22,706	17	127,671	103,027
Identifiable assets	5,077,137	4,499,251	5,077,137	4,499,251
Canada
Quarter ended:
Total revenues	32,876	32,480	122,864	121,440
Depreciation and amortization, net of (gains) losses on disposals	1,989	1,957	6,032	5,876
Interest expense	150	165	454	489
Pretax earnings	1,201	4,696	18,721	21,518
Income tax expense	318	1,384	4,961	6,340
Identifiable assets	$ 141,826	$ 134,751	$ 141,826	$ 134,751