CASH, CASH EQUIVALENTS AND INVESTMENTS (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents	$ 232,704	$ 228,776	$ 209,335	$ 277,373
Short-term investments (due in 1 year or less)	102,717	116,581
Long-term investments (due in 1 to 3 years)	100,342	80,261
Total cash, cash equivalents and investments measured at fair value, amortized cost	435,516	425,501
Total cash, cash equivalents and investments measured at fair value, gross unrealized gain	276	126
Total cash, cash equivalents and investments measured at fair value, gross unrealized loss	(29)	(9)
Total cash, cash equivalents and investments measured at fair value, fair value	435,763	425,618
Level 2
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents		4,900
Available-for-sale Securities, amortized cost basis	201,033	171,500
Available-for-sale Securities, gross unrealized gains	245	104
Available-for-sale Securities, gross unrealized losses	(26)	(9)
Available-for-sale Securities, fair value	201,252	171,595
Short-term investments (due in 1 year or less)	100,910	109,338
Long-term investments (due in 1 to 3 years)	100,342	57,357
Cash
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents	232,704	118,881
Mutual Funds | Level 1
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, amortized cost basis	1,779
Available-for-sale Securities, gross unrealized gains	31
Available-for-sale Securities, gross unrealized losses	(3)
Available-for-sale Securities, fair value	1,807
Short-term investments (due in 1 year or less)	1,807
Long-term investments (due in 1 to 3 years)	0
Government Agency Securities | Level 2
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, amortized cost basis	53,976
Available-for-sale Securities, gross unrealized gains	43
Available-for-sale Securities, gross unrealized losses	(9)
Available-for-sale Securities, fair value	54,010
Short-term investments (due in 1 year or less)	21,325
Long-term investments (due in 1 to 3 years)	32,685
US Treasury Bills and Government Securities | Level 1
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents		104,995
Available-for-sale Securities, amortized cost basis		135,120
Available-for-sale Securities, gross unrealized gains		22
Available-for-sale Securities, gross unrealized losses		0
Available-for-sale Securities, fair value		135,142
Short-term investments (due in 1 year or less)		7,243
Long-term investments (due in 1 to 3 years)		22,904
US Treasury Bills and Government Securities | Level 2
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents		0
Available-for-sale Securities, amortized cost basis		91,284
Available-for-sale Securities, gross unrealized gains		38
Available-for-sale Securities, gross unrealized losses		(4)
Available-for-sale Securities, fair value		91,318
Short-term investments (due in 1 year or less)		58,864
Long-term investments (due in 1 to 3 years)		32,454
Commercial Paper-not included in Cash and Cash Equivalents | Level 2
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, amortized cost basis	47,766	20,570
Available-for-sale Securities, gross unrealized gains	7	9
Available-for-sale Securities, gross unrealized losses	0	0
Available-for-sale Securities, fair value	47,773	20,579
Short-term investments (due in 1 year or less)	47,773	15,679
Long-term investments (due in 1 to 3 years)	0	0
Commercial Paper | Level 2
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents		4,900
Corporate Bonds | Level 2
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents		0
Available-for-sale Securities, amortized cost basis	98,289	58,644
Available-for-sale Securities, gross unrealized gains	195	54
Available-for-sale Securities, gross unrealized losses	(17)	(5)
Available-for-sale Securities, fair value	98,467	58,693
Short-term investments (due in 1 year or less)	30,810	34,795
Long-term investments (due in 1 to 3 years)	67,657	23,898
Certificates of Deposits (CDs) | Level 2
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents		0
Available-for-sale Securities, amortized cost basis	1,002	1,002
Available-for-sale Securities, gross unrealized gains	0	3
Available-for-sale Securities, gross unrealized losses	0	0
Available-for-sale Securities, fair value	1,002	1,005
Short-term investments (due in 1 year or less)	1,002	0
Long-term investments (due in 1 to 3 years)	$ 0	$ 1,005