Industry Segment and Geographic Area Data (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Fiscal year ended:
Total revenues	$ 3,074,531	$ 2,835,252	$ 2,558,587
Depreciation and amortization, net of (gains) losses on disposals	297,826	279,594	255,372
Interest expense	97,525	92,692	90,696
Pretax earnings	561,418	537,522	408,487
Income tax expense	204,677	195,131	143,779
Identifiable assets	6,872,175	5,998,978	5,306,601
United States [Member]
Fiscal year ended:
Total revenues	2,916,027	2,681,800	2,409,291
Depreciation and amortization, net of (gains) losses on disposals	292,345	272,236	247,413
Interest expense	96,979	92,128	90,137
Pretax earnings	541,371	516,207	389,342
Income tax expense	199,444	189,419	138,911
Identifiable assets	6,685,572	5,854,503	5,160,889
Canada [Member]
Fiscal year ended:
Total revenues	158,504	153,452	149,296
Depreciation and amortization, net of (gains) losses on disposals	5,481	7,358	7,959
Interest expense	546	564	559
Pretax earnings	20,047	21,315	19,145
Income tax expense	5,233	5,712	4,868
Identifiable assets	$ 186,603	$ 144,475	$ 145,712