Fair Value Disclosures Marketable securities, classified as "available-for-sale" (Details) (Fair Value, Inputs, Level 1 [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Mar. 31, 2013
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	$ 21,730	$ 16,596
Gross unrecognized holding losses	(79)	(8)
Fair value	$ 21,651	$ 16,588