Cash, Cash Equivalents and Investments with Hierarchy (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Amortized Costs	$ 177,198	$ 178,402
Gross Unrealized Gains	71	55
Gross Unrealized Loss	(175)	(96)
Estimated Fair Value	177,094us-gaap_AvailableForSaleSecurities	178,361us-gaap_AvailableForSaleSecurities
Cash and cash equivalents	53,110	59,159	50,305	22,426
Short-term marketable investments	123,984	47,181
Long-term marketable investments		72,021
Aavailable-for-sale investments due within one year	69,502
Aavailable-for-sale investments due after one year	54,482
Level 1
Amortized Costs	55,110	61,123
Gross Unrealized Gains	0	0
Gross Unrealized Loss	(107)	(55)
Estimated Fair Value	55,003	61,068
Cash and cash equivalents	53,110	59,159
Short-term marketable investments	1,893	1,909
Long-term marketable investments		0
Level 2
Amortized Costs	122,088	117,279
Gross Unrealized Gains	71	55
Gross Unrealized Loss	(68)	(41)
Estimated Fair Value	12,291	117,293
Cash and cash equivalents	0	0
Short-term marketable investments	122,091	45,272
Long-term marketable investments		72,021
Cash
Amortized Costs	24,734	26,548
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	24,734	26,548
Cash and cash equivalents	24,734	26,548
Short-term marketable investments	0	0
Long-term marketable investments		0
Money Market Funds \| Level 1
Amortized Costs	28,376	32,611
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Estimated Fair Value	28,376	32,611
Cash and cash equivalents	28,376	32,611
Short-term marketable investments	0	0
Long-term marketable investments		0
Mutual Funds \| Level 1
Amortized Costs	2,000	1,964
Gross Unrealized Gains	0	0
Gross Unrealized Loss	(107)	(55)
Estimated Fair Value	1,893	1,909
Cash and cash equivalents	0	0
Short-term marketable investments	1,893	1,909
Long-term marketable investments		0
Commercial Paper \| Level 2
Amortized Costs	9,043	30,374
Gross Unrealized Gains	1	5
Gross Unrealized Loss	0	0
Estimated Fair Value	9,044	30,379
Cash and cash equivalents	0	0
Short-term marketable investments	9,044	30,379
Long-term marketable investments		0
Corporate Debt \| Level 2
Amortized Costs	75,284	63,621
Gross Unrealized Gains	57	35
Gross Unrealized Loss	(10)	(39)
Estimated Fair Value	75,331	63,617
Cash and cash equivalents	0	0
Short-term marketable investments	75,331	14,893
Long-term marketable investments		48,724
Municipal Securities \| Level 2
Amortized Costs	5,435	5,435
Gross Unrealized Gains	2	5
Gross Unrealized Loss	(1)	(1)
Estimated Fair Value	5,436	5,439
Cash and cash equivalents	0	0
Short-term marketable investments	5,436	0
Long-term marketable investments		5,439
Asset-backed Securities \| Level 2
Amortized Costs	21,503	17,049
Gross Unrealized Gains	4	6
Gross Unrealized Loss	(5)	(1)
Estimated Fair Value	21,502	17,054
Cash and cash equivalents	0	0
Short-term marketable investments	21,502	0
Long-term marketable investments		17,054
Mortgage backed Securities \| Level 2
Amortized Costs	5,822
Gross Unrealized Gains	0
Gross Unrealized Loss	(52)
Estimated Fair Value	5,770
Cash and cash equivalents	0
Short-term marketable investments	5,770
Agency Bond \| Level 2
Amortized Costs	4,201
Gross Unrealized Gains	3
Gross Unrealized Loss	0
Estimated Fair Value	4,204
Cash and cash equivalents	0
Short-term marketable investments	4,204
International Government Securities \| Level 2
Amortized Costs	800	800
Gross Unrealized Gains	4	4
Gross Unrealized Loss	0	0
Estimated Fair Value	804	804
Cash and cash equivalents	0	0
Short-term marketable investments	804	0
Long-term marketable investments		$ 804

No authoritative reference available.

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