CASH, CASH EQUIVALENTS, AND INVESTMENTS (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2013	Mar. 31, 2013
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents	$ 235,250	$ 232,704	$ 256,343	$ 228,776
Short-term investments (due in 1 year or less)	93,187	102,717
Long-term investments (due in 1 to 3 years)	108,784	100,342
Total cash, cash equivalents and investments measured at fair value, amortized cost	436,800	435,516
Total cash, cash equivalents and investments measured at fair value, gross unrealized gains	431	276
Total cash, cash equivalents and investments measured at fair value, gross unrealized losses	(10)	(29)
Total cash, cash equivalents and investments measured at fair value, fair value	437,221	435,763
Cash [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents	230,752	232,704
Level 1 [Member] | Mutual Funds [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, amortized cost basis	3,418	1,779
Available-for-sale Securities, gross unrealized gains	126	31
Available-for-sale Securities, gross unrealized losses	0	(3)
Available-for-sale Securities, fair value	3,544	1,807
Short-term investments (due in 1 year or less)	3,544	1,807
Long-term investments (due in 1 to 3 years)	0	0
Level 2 [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents	4,498
Available-for-sale Securities, amortized cost basis	202,630	201,033
Available-for-sale Securities, gross unrealized gains	305	245
Available-for-sale Securities, gross unrealized losses	(10)	(26)
Available-for-sale Securities, fair value	202,925	201,252
Short-term investments (due in 1 year or less)	89,643	100,910
Long-term investments (due in 1 to 3 years)	108,784	100,342
Level 2 [Member] | Government Agency Securities [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, amortized cost basis	51,329	53,976
Available-for-sale Securities, gross unrealized gains	48	43
Available-for-sale Securities, gross unrealized losses	(7)	(9)
Available-for-sale Securities, fair value	51,370	54,010
Short-term investments (due in 1 year or less)	5,812	21,325
Long-term investments (due in 1 to 3 years)	45,558	32,685
Level 2 [Member] | Commercial Paper [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and cash equivalents	4,498
Available-for-sale Securities, amortized cost basis	55,762	47,766
Available-for-sale Securities, gross unrealized gains	12	7
Available-for-sale Securities, gross unrealized losses	0	0
Available-for-sale Securities, fair value	55,774	47,773
Short-term investments (due in 1 year or less)	51,276	47,773
Long-term investments (due in 1 to 3 years)	0	0
Level 2 [Member] | Corporate Bonds [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, amortized cost basis	94,537	98,289
Available-for-sale Securities, gross unrealized gains	245	195
Available-for-sale Securities, gross unrealized losses	(3)	(17)
Available-for-sale Securities, fair value	94,779	98,467
Short-term investments (due in 1 year or less)	31,553	30,810
Long-term investments (due in 1 to 3 years)	63,226	67,657
Level 2 [Member] | Certificates of Deposits (CDs) [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale Securities, amortized cost basis	1,002	1,002
Available-for-sale Securities, gross unrealized gains	0	0
Available-for-sale Securities, gross unrealized losses	0	0
Available-for-sale Securities, fair value	1,002	1,002
Short-term investments (due in 1 year or less)	1,002	1,002
Long-term investments (due in 1 to 3 years)	$ 0	$ 0