Transactions under 1999 Stock Option Plan and 2007 Equity Incentive Plan (Detail) (USD $)	12 Months Ended
Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Stock option Plan
Stock Options, Number of Shares, Beginning balance	240,892	325,519	813,741
Stock Options, Number of Shares, Granted	0	0	0
Stock Options, Number of Shares, Exercised	(86,892)	(84,502)	(450,432)
Stock Options, Number of Shares, Canceled	0	(125)	(37,790)
Stock Options, Number of Shares, Ending balance	154,000	240,892	325,519
Stock Option, Weighted Average Exercise Price
Stock Options, Weighted Average Exercise Price, Beginning balance	$ 6.63	$ 6.35	$ 7.60
Stock Options, Weighted Average Exercise Price, Granted	$ 0	$ 0	$ 0
Stock Options, Weighted Average Exercise Price, Exercised	$ 6.62	$ 5.58	$ 7.50
Stock Options, Weighted Average Exercise Price, Canceled	$ 0	$ 5.26	$ 19.42
Stock Options, Weighted Average Exercise Price, Ending balance	$ 6.63	$ 6.63	$ 6.35
Restricted Stock Units, Number of Awards
Restricted Stock Units, Number of Awards, Beginning balance	1,755,325	1,418,859	1,112,376
Restricted Stock Units, Number of Awards, Granted	764,893	1,071,131	928,596
Restricted Stock Units, Number of Awards, Issued	(549,932)	(659,350)	(504,393)
Restricted Stock Units, Number of Awards, Canceled	(99,460)	(75,315)	(117,720)
Restricted Stock Units, Number of Awards, Ending balance	1,871,148	1,755,325	1,418,859
Restricted Stock Units, Weighted Average Fair Value
Restricted Stock Units, Weighted Average Fair Value, Beginning balance	$ 13.33	$ 12.35	$ 9.96
Restricted Stock Units, Weighted Average Fair Value, Granted	$ 24.19	$ 13.36	$ 13.67
Restricted Stock Units, Weighted Average Fair Value, Issued	$ 12.52	$ 11.26	$ 10.81
Restricted Stock Units, Weighted Average Fair Value, Canceled	$ 16.10	$ 13.60	$ 9.87
Restricted Stock Units, Weighted Average Fair Value, Ending balance	$ 17.85	$ 13.33	$ 12.35

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Net number of share options (or share units) granted during the period.

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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No definition available.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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No definition available.

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Weighted average price at which grantees can acquire the shares reserved for issuance on stock options awarded.

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Number of share options (or share units) exercised during the current period.

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