Interest Rate Swap Agreements - Summary of activity in company's notional amounts of interest rate swap agreements (Details) (Interest Rate Swap, USD $)	6 Months Ended
Sep. 30, 2013	Sep. 30, 2012
Interest Rate Swap
Derivatives Fair Value [Roll Forward]
Notional amounts at April 1	$ 50,000,000
New contracts		50,000,000
Matured contracts
Notional amounts at September 30	$ 50,000,000	$ 50,000,000

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant