Industry Segment and Geographic Area Data (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Fiscal year ended:
Total revenues	$ 2,835,252	$ 2,558,587	$ 2,512,027
Depreciation and amortization, net of (gains) losses on disposals	279,594	255,372	222,692
Interest expense	92,692	90,696	90,371
Pretax earnings	537,522	408,487	325,636
Income tax expense	195,131	143,779	120,269
Identifiable assets	5,998,978	5,306,601	4,654,051
United States [Member]
Fiscal year ended:
Total revenues	2,681,800	2,409,291	2,364,560
Depreciation and amortization, net of (gains) losses on disposals	272,236	247,413	214,800
Interest expense	92,128	90,137	89,730
Pretax earnings	516,207	389,342	302,748
Income tax expense	189,419	138,911	114,050
Identifiable assets	5,854,545	5,160,889	4,518,772
Canada [Member]
Fiscal year ended:
Total revenues	153,452	149,296	147,467
Depreciation and amortization, net of (gains) losses on disposals	7,358	7,959	7,892
Interest expense	564	559	641
Pretax earnings	21,315	19,145	22,888
Income tax expense	5,712	4,868	6,219
Identifiable assets	$ 144,475	$ 145,712	$ 135,279