Certain Financial Statement Information Cost and Fair Value of Available-for-Sale Securities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Mar. 31, 2013
Schedule of cost and estimated fair values of available-for-sale securities with stated maturities by contractual maturity
Less than 1 year, Cost	$ 7,259	$ 9,205
Mature in 1 - 2 years, Cost	22,341	19,843
Mature in 3 - 5 years, Cost	707	1,575
Mature after 5 years, Cost	937	962
Cost, Total	31,244	31,585
Less than 1 year, Fair Value	7,411	9,217
Mature in 1 - 2 years, Fair Value	22,369	20,040
Mature in 3 - 5 years, Fair Value	771	1,649
Mature after 5 years, Fair Value	1,002	1,098
Fair Value, Total	$ 31,553	$ 32,004