CASH, CASH EQUIVALENTS, AND INVESTMENTS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash and Cash Equivalents, Fair Value	$ 235,534	$ 228,776	$ 196,656	$ 209,335
Cash, Cash Equivalents Before Unrealized Gains And Losses, and Amortized Cost Basis of Available-For-Sale Securities	428,608	425,501
Cash Equivalents and Available-For-Sale Securities, Gross Unrealized Gains	166	126
Cash Equivalents and Available-For-Sale Securities, Gross Unrealized Losses	(43)	(9)
Cash and Fair Value of Cash Equivalents and Available-For-Sale Securities	428,731	425,618
U.S. Treasury Bills and Government Agency Securities [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, gross unrealized gains	23	42
Available-for-sale securities, gross unrealized losses	(14)	(1)
Available-for-sale securities, Long-term investments (due in 1 to 3 years), Amortized Cost	36,929	55,317
Available-for-sale securities, Long term investments (due in 1 to 3 years), Fair Value	36,938	55,358
Corporate Bonds [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, gross unrealized gains	116	23
Available-for-sale securities, gross unrealized losses	(26)	(3)
Available-for-sale securities, Long-term investments (due in 1 to 3 years), Amortized Cost	69,772	23,878
Available-for-sale securities, Long term investments (due in 1 to 3 years), Fair Value	69,862	23,898
Certificates of Deposit [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, gross unrealized gains	0	3
Available-for-sale securities, gross unrealized losses	0	0
Available-for-sale securities, Long-term investments (due in 1 to 3 years), Amortized Cost	0	1,002
Available-for-sale securities, Long term investments (due in 1 to 3 years), Fair Value	0	1,005
U.S. Treasury Bills and Government Agency Securities [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, Short-term investments (due in 1 year or less), Amortized Cost	19,227	66,092
Available-for-sale securities, gross unrealized gains	6	18
Available-for-sale securities, gross unrealized losses	(1)	(3)
Available-for-sale securities, Short-term investments (due in 1 year or less), Fair Value	19,232	66,107
Commercial Paper [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, Short-term investments (due in 1 year or less), Amortized Cost	43,792	15,670
Available-for-sale securities, gross unrealized gains	13	9
Available-for-sale securities, gross unrealized losses	0	0
Available-for-sale securities, Short-term investments (due in 1 year or less), Fair Value	43,805	15,679
Corporate Bonds [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, Short-term investments (due in 1 year or less), Amortized Cost	22,353	34,766
Available-for-sale securities, gross unrealized gains	6	31
Available-for-sale securities, gross unrealized losses	(2)	(2)
Available-for-sale securities, Short-term investments (due in 1 year or less), Fair Value	22,357	34,795
Certificates of Deposit [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, Short-term investments (due in 1 year or less), Amortized Cost	1,002	0
Available-for-sale securities, gross unrealized gains	1	0
Available-for-sale securities, gross unrealized losses	0	0
Available-for-sale securities, Short-term investments (due in 1 year or less), Fair Value	1,003	0
Cash [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash	225,310	118,881
Cash Equivalents [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Cash Equivalents Before Unrealized Gains And Losses	10,223	109,895
Cash Equivalents, Gross Unrealized Gains	1	0
Cash Equivalents, Gross Unrealized Losses	0	0
Cash equivalents, fair value	10,224	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	235,533	228,776
Cash Equivalents, Gross Unrealized Gains	1	0
Cash Equivalents, Gross Unrealized Losses	0	0
Cash and Cash Equivalents, Fair Value	235,534	228,776
Short-term Investments [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, Short-term investments (due in 1 year or less), Amortized Cost	86,374	116,528
Available-for-sale securities, gross unrealized gains	26	58
Available-for-sale securities, gross unrealized losses	(3)	(5)
Available-for-sale securities, Short-term investments (due in 1 year or less), Fair Value	86,397	116,581
Long-term investments [Member]
Schedule of Cash, Cash Equivalents and Investments [Line Items]
Available-for-sale securities, gross unrealized gains	139	68
Available-for-sale securities, gross unrealized losses	(40)	(4)
Available-for-sale securities, Long-term investments (due in 1 to 3 years), Amortized Cost	106,701	80,197
Available-for-sale securities, Long term investments (due in 1 to 3 years), Fair Value	$ 106,800	$ 80,261