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Interest Rate Swap Agreements - Summary of the activity in the company's notional amounts of interest rate swap agreements (Details) (Interest Rate Swap, USD $) | 12 Months Ended
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Mar. 31, 2013 | Mar. 31, 2012 | Mar. 31, 2011
Interest Rate Swap |  |  |
Derivatives Fair Value [Roll Forward] |  |  |
Notional amounts at beginning of year |  |  | $ 50,000,000
New contracts | 50,000,000 |  |
Matured contracts |  |  | (50,000,000)
Notional amounts at end of year | $ 50,000,000 |  |

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Additions of notional amount of interest rate fair value hedge derivatives during period. + References No definition available. + Details
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- Details
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- Definition Maturities of interest rate fair value hedge derivatives during period. + References No definition available. + Details
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