Cash, Cash Equivalents and Investments with Hierarchy (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Amortized Costs	$ 175,191	$ 163,005
Gross Unrealized Gains	73	89
Gross Unrealized Loss	(275)	(244)
Estimated Fair Value	174,989	162,850
Cash and cash equivalents	41,030	33,576	$ 53,110	$ 59,159
Short-term marketable investments	133,959	129,274
Liabilities, Fair Value Disclosure	148	341	$ 0
Aavailable-for-sale investments due within one year	78,039
Aavailable-for-sale investments due after one year	55,920
Level 1
Amortized Costs	43,030	35,576
Gross Unrealized Gains	0	0
Gross Unrealized Loss	(194)	(187)
Estimated Fair Value	42,836	35,389
Cash and cash equivalents	41,030	33,576
Short-term marketable investments	1,806	1,813
Level 2
Amortized Costs	132,161	127,429
Gross Unrealized Gains	73	89
Gross Unrealized Loss	(81)	(57)
Estimated Fair Value	132,153	127,461
Cash and cash equivalents	0	0
Short-term marketable investments	132,153	127,461
Level 3
Amortized Costs	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	148	341
Cash and cash equivalents	0	0
Short-term marketable investments	0	0
Liabilities, Fair Value Disclosure	148	341
Cash
Amortized Costs	29,122	18,596
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	29,122	18,596
Cash and cash equivalents	29,122	18,596
Short-term marketable investments	0	0
Money Market Funds | Level 1
Amortized Costs	11,908	14,980
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	11,908	14,980
Cash and cash equivalents	11,908	14,980
Short-term marketable investments	0	0
Mutual Funds | Level 1
Amortized Costs	2,000	2,000
Gross Unrealized Gains	0	0
Gross Unrealized Loss	(194)	(187)
Estimated Fair Value	1,806	1,813
Cash and cash equivalents	0	0
Short-term marketable investments	1,806	1,813
Commercial Paper | Level 2
Amortized Costs	19,144	6,794
Gross Unrealized Gains	8	2
Gross Unrealized Loss	0	0
Estimated Fair Value	19,152	6,796
Cash and cash equivalents	0	0
Short-term marketable investments	19,152	6,796
Corporate Debt | Level 2
Amortized Costs	83,995	85,164
Gross Unrealized Gains	61	78
Gross Unrealized Loss	(58)	(28)
Estimated Fair Value	83,998	85,214
Cash and cash equivalents	0	0
Short-term marketable investments	83,998	85,214
Municipal Securities | Level 2
Amortized Costs		1,007
Gross Unrealized Gains		0
Gross Unrealized Loss		(1)
Estimated Fair Value		1,006
Cash and cash equivalents		0
Short-term marketable investments		1,006
Asset-backed Securities | Level 2
Amortized Costs	26,906	24,614
Gross Unrealized Gains	4	7
Gross Unrealized Loss	(22)	(11)
Estimated Fair Value	26,888	24,610
Cash and cash equivalents	0	0
Short-term marketable investments	26,888	24,610
Mortgage backed Securities | Level 2
Amortized Costs	116	2,045
Gross Unrealized Gains	0	0
Gross Unrealized Loss	(1)	(17)
Estimated Fair Value	115	2,028
Cash and cash equivalents	0	0
Short-term marketable investments	115	2,028
Agency Bond | Level 2
Amortized Costs	2,000	6,805
Gross Unrealized Gains	0	1
Gross Unrealized Loss	0	0
Estimated Fair Value	2,000	6,806
Cash and cash equivalents	0	0
Short-term marketable investments	2,000	6,806
International Government Securities | Level 2
Amortized Costs		1,000
Gross Unrealized Gains		1
Gross Unrealized Loss		0
Estimated Fair Value		1,001
Cash and cash equivalents		0
Short-term marketable investments		1,001
Contingent Consideration | Level 3
Amortized Costs	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	148	341
Cash and cash equivalents	0	0
Short-term marketable investments	0	0
Liabilities, Fair Value Disclosure	$ 148	$ 341