Financial Information by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Fiscal year ended:
Total revenues	$ 3,275,656	$ 3,074,531	$ 2,835,252
Depreciation and amortization, net of (gains) losses on disposals	313,962	297,826	279,594
Interest expense	97,903	97,525	92,692
Pretax earnings	768,911	561,418	537,522
Income tax expense	279,910	204,677	195,131
Identifiable assets	8,150,725	6,872,175	5,998,978
United States [Member]
Fiscal year ended:
Total revenues	3,130,097	2,916,027	2,681,800
Depreciation and amortization, net of (gains) losses on disposals	313,099	292,345	272,236
Interest expense	97,739	96,979	92,128
Pretax earnings	745,194	541,371	516,207
Income tax expense	273,473	199,444	189,419
Identifiable assets	7,901,365	6,685,572	5,854,503
Canada [Member]
Fiscal year ended:
Total revenues	145,559	158,504	153,452
Depreciation and amortization, net of (gains) losses on disposals	863	5,481	7,358
Interest expense	164	546	564
Pretax earnings	23,717	20,047	21,315
Income tax expense	6,437	5,233	5,712
Identifiable assets	$ 249,360	$ 186,603	$ 144,475