Cash, Cash Equivalents and Investments with Hierarchy (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Mar. 31, 2016
Amortized Costs	$ 167,012	$ 175,191
Gross Unrealized Gains	68	73
Gross Unrealized Loss	(30)	(275)
Estimated Fair Value	167,050	174,989
Cash and cash equivalents	34,570	41,030	$ 32,094	$ 33,576
Short-term marketable investments	132,480	133,959
Liabilities, Fair Value Disclosure		148
Aavailable-for-sale investments due within one year	80,612
Aavailable-for-sale investments due after one year	51,868
Level 1
Amortized Costs	36,398	43,030
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	(194)
Estimated Fair Value	36,398	42,836
Cash and cash equivalents	34,570	41,030
Short-term marketable investments	1,828	1,806
Level 2
Amortized Costs	130,614	132,161
Gross Unrealized Gains	68	73
Gross Unrealized Loss	(30)	(81)
Estimated Fair Value	130,652	132,153
Cash and cash equivalents	0	0
Short-term marketable investments	130,652	132,153
Level 3
Amortized Costs		0
Gross Unrealized Gains		0
Gross Unrealized Loss		0
Estimated Fair Value		148
Cash and cash equivalents		0
Short-term marketable investments		0
Liabilities, Fair Value Disclosure		148
Cash
Amortized Costs	20,122	29,122
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	20,122	29,122
Cash and cash equivalents	20,122	29,122
Short-term marketable investments	0	0
Money Market Funds | Level 1
Amortized Costs	14,448	11,908
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	14,448	11,908
Cash and cash equivalents	14,448	11,908
Short-term marketable investments	0	0
Mutual Funds | Level 1
Amortized Costs	1,828	2,000
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	(194)
Estimated Fair Value	1,828	1,806
Cash and cash equivalents	0	0
Short-term marketable investments	1,828	1,806
Commercial Paper | Level 2
Amortized Costs	13,554	19,144
Gross Unrealized Gains	2	8
Gross Unrealized Loss	0	0
Estimated Fair Value	13,556	19,152
Cash and cash equivalents	0	0
Short-term marketable investments	13,556	19,152
Corporate Debt | Level 2
Amortized Costs	88,578	83,995
Gross Unrealized Gains	62	61
Gross Unrealized Loss	(21)	(58)
Estimated Fair Value	88,619	83,998
Cash and cash equivalents	0	0
Short-term marketable investments	88,619	83,998
International Government Securities | Level 2
Amortized Costs	2,494
Gross Unrealized Gains	0
Gross Unrealized Loss	(1)
Estimated Fair Value	2,493
Cash and cash equivalents	0
Short-term marketable investments	2,493
Asset-backed Securities | Level 2
Amortized Costs	25,988	26,906
Gross Unrealized Gains	4	4
Gross Unrealized Loss	(8)	(22)
Estimated Fair Value	25,984	26,888
Cash and cash equivalents	0	0
Short-term marketable investments	$ 25,984	26,888
Mortgage backed Securities | Level 2
Amortized Costs		116
Gross Unrealized Gains		0
Gross Unrealized Loss		(1)
Estimated Fair Value		115
Cash and cash equivalents		0
Short-term marketable investments		115
Agency Bond | Level 2
Amortized Costs		2,000
Gross Unrealized Gains		0
Gross Unrealized Loss		0
Estimated Fair Value		2,000
Cash and cash equivalents		0
Short-term marketable investments		2,000
Contingent Consideration | Level 3
Amortized Costs		0
Gross Unrealized Gains		0
Gross Unrealized Loss		0
Estimated Fair Value		148
Cash and cash equivalents		0
Short-term marketable investments		0
Liabilities, Fair Value Disclosure		$ 148