Marketable Securities (Summary of available-for-sale securities ) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 2,050	$ 1,138
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	4,871
Aggregate fair value	2,050	6,009
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,475	18,080
Gross Unrealized Gains	248	253
Gross Unrealized Losses	37	147
Estimated Fair Value	7,686	18,186
Securities in a continuous loss position for less than 12 months	37	58
Securities in a continuous loss position for more than 12 months	0	89
Unrealized losses	$ 37	$ 147