Cash, Cash Equivalents and Investments with Hierarchy (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Amortized Costs	$ 163,005	$ 177,198
Gross Unrealized Gains	89	71
Gross Unrealized Loss	(244)	(175)
Estimated Fair Value	162,850	177,094
Cash and cash equivalents	33,576	53,110	$ 59,159	$ 50,305
Short-term marketable investments	129,274	123,984
Liabilities, Fair Value Disclosure	341	0	$ 0
Aavailable-for-sale investments due within one year	71,071
Aavailable-for-sale investments due after one year	58,203
Level 1
Amortized Costs	35,576	55,110
Gross Unrealized Gains	0	0
Gross Unrealized Loss	(187)	(107)
Estimated Fair Value	35,389	55,003
Cash and cash equivalents	33,576	53,110
Short-term marketable investments	1,813	1,893
Level 2
Amortized Costs	127,429	122,088
Gross Unrealized Gains	89	71
Gross Unrealized Loss	(57)	(68)
Estimated Fair Value	127,461	122,091
Cash and cash equivalents	0	0
Short-term marketable investments	127,461	122,091
Level 3
Amortized Costs	0
Gross Unrealized Gains	0
Gross Unrealized Loss	0
Estimated Fair Value	341
Cash and cash equivalents	0
Short-term marketable investments	0
Liabilities, Fair Value Disclosure	341
Cash
Amortized Costs	18,596	24,734
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	18,596	24,734
Cash and cash equivalents	18,596	24,734
Short-term marketable investments	0	0
Money Market Funds | Level 1
Amortized Costs	14,980	28,376
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	14,980	28,376
Cash and cash equivalents	14,980	28,376
Short-term marketable investments	0	0
Mutual Funds | Level 1
Amortized Costs	2,000	2,000
Gross Unrealized Gains	0	0
Gross Unrealized Loss	(187)	(107)
Estimated Fair Value	1,813	1,893
Cash and cash equivalents	0	0
Short-term marketable investments	1,813	1,893
Commercial Paper | Level 2
Amortized Costs	6,794	9,043
Gross Unrealized Gains	2	1
Gross Unrealized Loss	0	0
Estimated Fair Value	6,796	9,044
Cash and cash equivalents	0	0
Short-term marketable investments	6,796	9,044
Corporate Debt | Level 2
Amortized Costs	85,164	75,284
Gross Unrealized Gains	78	57
Gross Unrealized Loss	(28)	(10)
Estimated Fair Value	85,214	75,331
Cash and cash equivalents	0	0
Short-term marketable investments	85,214	75,331
Municipal Securities | Level 2
Amortized Costs	1,007	5,435
Gross Unrealized Gains	0	2
Gross Unrealized Loss	(1)	(1)
Estimated Fair Value	1,006	5,436
Cash and cash equivalents	0	0
Short-term marketable investments	1,006	5,436
Asset-backed Securities | Level 2
Amortized Costs	24,614	21,503
Gross Unrealized Gains	7	4
Gross Unrealized Loss	(11)	(5)
Estimated Fair Value	24,610	21,502
Cash and cash equivalents	0	0
Short-term marketable investments	24,610	21,502
Mortgage backed Securities | Level 2
Amortized Costs	2,045	5,822
Gross Unrealized Gains	0	0
Gross Unrealized Loss	(17)	(52)
Estimated Fair Value	2,028	5,770
Cash and cash equivalents	0	0
Short-term marketable investments	2,028	5,770
Agency Bond | Level 2
Amortized Costs	6,805	4,201
Gross Unrealized Gains	1	3
Gross Unrealized Loss	0	0
Estimated Fair Value	6,806	4,204
Cash and cash equivalents	0	0
Short-term marketable investments	6,806	4,204
International Government Securities | Level 2
Amortized Costs	1,000	800
Gross Unrealized Gains	1	4
Gross Unrealized Loss	0	0
Estimated Fair Value	1,001	804
Cash and cash equivalents	0	0
Short-term marketable investments	1,001	$ 804
Contingent Consideration | Level 3
Amortized Costs	0
Gross Unrealized Gains	0
Gross Unrealized Loss	0
Estimated Fair Value	341
Cash and cash equivalents	0
Short-term marketable investments	0
Liabilities, Fair Value Disclosure	$ 341