Roll Forward Of Other-Than-Temporary Impairment Related To Credit Losses (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Beginning balance of unrealized OTTI related to credit losses	$ 2,391	$ 2,197
Additional unrealized OTTI related to credit losses for which OTTI was previously recognized	412	558
Credit related OTTI previously recognized for securities sold during the period	(1,075)
Credit related OTTI previously recognized for securities paid-off during the period	(4)
Decrease for realized amount of credit losses for which unrealized credit related OTTI was previously recognized	(722)	(364)
Ending balance of unrealized OTTI related to credit losses	$ 1,002	$ 2,391

The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity).

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This item represents reductions in the amount of cumulative losses recognized in earnings for other than temporary impairments (OTTI) for which a portion of the impairment had been recognized in other comprehensive income (a component of shareholders' equity) due to a change in status of the impaired security because of a change in the entity's intent to either sell the impaired security or it has become more likely than not that the entity will be required to sell the security before recovery of its cost basis.

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