Share-Based Compensation (Details 1) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Aug. 31, 2012
Options outstanding, range of exercise prices and remaining contractual lives
No. of Options	1,505
Weighted Average Exercise Price	$ 19.36
Weighted Average Remaining Life	3 years 10 months 24 days
$0.00 to $3.21 [Member]
Options outstanding, range of exercise prices and remaining contractual lives
Range of Prices, Lower limit	$ 0.00
Range of Prices, Upper limit	$ 3.21
No. of Options
Weighted Average Exercise Price
Weighted Average Remaining Life
$3.22 to $6.41 [Member]
Options outstanding, range of exercise prices and remaining contractual lives
Range of Prices, Lower limit	$ 3.22
Range of Prices, Upper limit	$ 6.41
No. of Options	41
Weighted Average Exercise Price	$ 4.07
Weighted Average Remaining Life	1 year
$6.42 to $9.62 [Member]
Options outstanding, range of exercise prices and remaining contractual lives
Range of Prices, Lower limit	$ 6.42
Range of Prices, Upper limit	$ 9.62
No. of Options	260
Weighted Average Exercise Price	$ 8.63
Weighted Average Remaining Life	2 years 6 months
$9.63 to $12.82 [Member]
Options outstanding, range of exercise prices and remaining contractual lives
Range of Prices, Lower limit	$ 9.63
Range of Prices, Upper limit	$ 12.82
No. of Options	157
Weighted Average Exercise Price	$ 11.10
Weighted Average Remaining Life	3 years 4 months 24 days
$12.83 to $16.03 [Member]
Options outstanding, range of exercise prices and remaining contractual lives
Range of Prices, Lower limit	$ 12.83
Range of Prices, Upper limit	$ 16.03
No. of Options	431
Weighted Average Exercise Price	$ 14.83
Weighted Average Remaining Life	3 years 10 months 24 days
$16.04 to $32.05 [Member]
Options outstanding, range of exercise prices and remaining contractual lives
Range of Prices, Lower limit	$ 16.04
Range of Prices, Upper limit	$ 32.05
No. of Options	616
Weighted Average Exercise Price	$ 30.16
Weighted Average Remaining Life	5 years