Condensed Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2011	Nov. 30, 2010
Sales:
Sales from products	$ 315,047	$ 312,953	$ 642,945	$ 594,709
Sales from services	160,855	127,569	312,247	250,206
Total sales	475,902	440,522	955,192	844,915
Costs and operating expenses:
Cost of products	278,064	269,382	565,426	506,591
Cost of services	120,682	97,462	237,770	194,645
Selling, general and administrative	43,134	40,874	84,864	82,116
Total cost and operating expenses	441,880	407,718	888,060	783,352
Earnings from joint ventures	259	2,529	464	2,557
Operating income	34,281	35,333	67,596	64,120
Gain on extinguishment of debt				97
Interest expense	(7,869)	(7,579)	(15,387)	(15,012)
Interest income	335	76	439	236
Income from continuing operations before provision for income taxes	26,747	27,830	52,648	49,441
Provision for income taxes	9,228	9,740	18,166	17,304
Income from continuing operations	17,519	18,090	34,482	32,137
Discontinued operations, net of tax	13	(1,276)	(301)	(1,649)
Net income	$ 17,532	$ 16,814	$ 34,181	$ 30,488
Earnings per share - basic:
Earnings from continuing operations (in dollars per share)	$ 0.44	$ 0.47	$ 0.86	$ 0.84
Income (Loss) from discontinued operations (in dollars per share)	$ 0.00	$ (0.03)	$ (0.01)	$ (0.04)
Earnings per share - basic (in dollars per share)	$ 0.44	$ 0.44	$ 0.85	$ 0.80
Earnings per share - diluted:
Earnings from continuing operations (in dollars per share)	$ 0.43	$ 0.45	$ 0.84	$ 0.81
Income (loss) from discontinued operations (in dollars per share)	$ 0.00	$ (0.03)	$ (0.01)	$ (0.04)
Earnings per share - diluted (in dollars per share)	$ 0.43	$ 0.42	$ 0.83	$ 0.77