Computation of Earnings per Common Share (Details) (USD $) In Thousands, except Share data	3 Months Ended	6 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Basic earnings per share:
Numerator: Net income	$ 22,679	$ 25,992	$ 39,664	$ 38,637
Denominator:
Weighted-average common shares outstanding	218,521	221,280	218,373	222,900
Basic earnings per share	$ 0.10	$ 0.12	$ 0.18	$ 0.17
Diluted earnings per share:
Numerator: Net income	$ 22,679	$ 25,992	$ 39,664	$ 38,637
Denominator:
Weighted-average common shares outstanding	218,521	221,280	218,373	222,900
Dilutive effect of stock awards	3,604	3,114	4,439	3,071
Total shares	222,125	224,394	222,812	225,971
Diluted earnings per share	$ 0.10	$ 0.12	$ 0.18	$ 0.17
Anti-dilutive shares related to stock awards excluded from EPS calculation (in shares)	14,100,000	19,600,000	8,400,000	19,900,000

Calculation of denominator for basic EPS.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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