CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES Components of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	$ 116,693	$ 54,141
Unrealized Gains (Losses)	25	20
Fair Value	116,718	54,161
U.S. government and municipal obligations
Cash, Cash Equivalents and Marketable Securities [Line Items]
Fair Value	91,757	31,645
Commercial paper
Cash, Cash Equivalents and Marketable Securities [Line Items]
Fair Value	14,581	12,390
Corporate bonds
Cash, Cash Equivalents and Marketable Securities [Line Items]
Fair Value	10,380	5,166
Certificates of deposit
Cash, Cash Equivalents and Marketable Securities [Line Items]
Fair Value	0	4,960
Short-term marketable securities
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	75,207	37,325
Unrealized Gains (Losses)	27	13
Fair Value	75,234	37,338
Short-term marketable securities | U.S. government and municipal obligations
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	53,854	17,416
Unrealized Gains (Losses)	26	11
Fair Value	53,880	17,427
Short-term marketable securities | Commercial paper
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	14,581	12,390
Unrealized Gains (Losses)	0	0
Fair Value	14,581	12,390
Short-term marketable securities | Corporate bonds
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	6,772	2,559
Unrealized Gains (Losses)	1	2
Fair Value	6,773	2,561
Short-term marketable securities | Certificates of deposit
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost		4,960
Unrealized Gains (Losses)		0
Fair Value		4,960
Long-term marketable securities
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	41,486	16,816
Unrealized Gains (Losses)	(2)	7
Fair Value	41,484	16,823
Long-term marketable securities | U.S. government and municipal obligations
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	37,875	14,211
Unrealized Gains (Losses)	2	7
Fair Value	37,877	14,218
Long-term marketable securities | Corporate bonds
Cash, Cash Equivalents and Marketable Securities [Line Items]
Amortized Cost	3,611	2,605
Unrealized Gains (Losses)	(4)	0
Fair Value	$ 3,607	$ 2,605