CASH, CASH EQUIVALENTS, AND INVESTMENTS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012	Mar. 31, 2012
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and Cash Equivalents, Fair Value	$ 256,343	$ 228,776	$ 204,639	$ 209,335
Cash, Cash Equivalents Before Unrealized Gains And Losses, and Amortized Cost Basis of Available-For-Sale Securities	443,953	425,501
Cash Equivalents and Available-For-Sale Securities, Gross Unrealized Gains	76	126
Cash Equivalents and Available-For-Sale Securities, Gross Unrealized Losses	(172)	(9)
Cash and Fair Value of Cash Equivalents and Available-For-Sale Securities	443,857	425,618
Available for Sale Securities, Debt Maturities [Abstract]
Due in 1 year or less (amortized cost)	115,621	226,423
Due in 1 to 3 years (amortized cost)	85,984	80,197
Due in 1 year or less (fair value)	115,605	226,476
Due in 1 to 3 years (fair value)	85,904	80,261
Total amortized cost	201,605	306,620
Total fair value	201,509	306,737
U.S. Treasury Bills and Government Agency Securities [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, amortized cost basis	42,892	55,317
Available-for-sale securities, gross unrealized gains	19	42
Available-for-sale securities, gross unrealized losses	(10)	(1)
Available-for-sale securities, fair value	42,901	55,358
Corporate Bonds [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, amortized cost basis	42,089	23,878
Available-for-sale securities, gross unrealized gains	12	23
Available-for-sale securities, gross unrealized losses	(102)	(3)
Available-for-sale securities, fair value	41,999	23,898
Certificates of Deposit [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	2	3
Available-for-sale securities, gross unrealized losses	0	0
Available-for-sale securities, fair value	1,004	1,005
U.S. Treasury Bills and Government Agency Securities [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, amortized cost basis	37,465	66,092
Available-for-sale securities, gross unrealized gains	9	18
Available-for-sale securities, gross unrealized losses	(57)	(3)
Available-for-sale securities, fair value	37,417	66,107
Commercial Paper [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, amortized cost basis	39,743	15,670
Available-for-sale securities, gross unrealized gains	16	9
Available-for-sale securities, gross unrealized losses	(1)	0
Available-for-sale securities, fair value	39,758	15,679
Corporate Bonds [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, amortized cost basis	24,419	34,766
Available-for-sale securities, gross unrealized gains	18	31
Available-for-sale securities, gross unrealized losses	(2)	(2)
Available-for-sale securities, fair value	24,435	34,795
Cash [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash	242,348	118,881
Cash Equivalents [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash Equivalents Before Unrealized Gains And Losses	13,995	109,895
Cash Equivalents, Gross Unrealized Gains	0	0
Cash Equivalents, Gross Unrealized Losses	0	0
Cash equivalents, fair value	13,995	109,895
Cash and cash equivalents [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and Cash Equivalents Before Unrealized Gains And Losses	256,343	228,776
Cash Equivalents, Gross Unrealized Gains	0	0
Cash Equivalents, Gross Unrealized Losses	0	0
Cash and Cash Equivalents, Fair Value	256,343	228,776
Short-term Investments [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, amortized cost basis	101,627	116,528
Available-for-sale securities, gross unrealized gains	43	58
Available-for-sale securities, gross unrealized losses	(60)	(5)
Available-for-sale securities, fair value	101,610	116,581
Long-term investments [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, amortized cost basis	85,983	80,197
Available-for-sale securities, gross unrealized gains	33	68
Available-for-sale securities, gross unrealized losses	(112)	(4)
Available-for-sale securities, fair value	$ 85,904	$ 80,261