Marketable Securities (Summary of available-for-sale securities ) (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Mar. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Marketable Securities, Realized Gain (Loss)	$ 21,000	$ 226,000	$ 115,000	$ 233,000
Aggregate Fair Value, Securities in a continuous loss position for less than 12 months	1,171,000		1,171,000
Aggregate Fair Value, Securities in a continuous loss position for more than 12 months	0		0
Aggregate Fair Value	1,171,000		1,171,000
Unrealized Losses, Securities in a continuous loss position for less than 12 months			2,000
Unrealized Losses, Securities in a continuous loss position for more than 12 months			0
Unrealized Losses			2,000
Foreign exchange contracts
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,210,000		9,210,000		$ 18,080,000
Gross Unrealized Gains	274,000				253,000
Gross Unrealized Losses	2,000				147,000
Estimated Fair Value	$ 9,482,000		$ 9,482,000		$ 18,186,000