Certain Financial Statement Information (Details 9) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Mar. 31, 2013		Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost method investment, ownership percentage (less than)	20.00%
Investments in non-marketable equity investments, cost method	$ 0		$ 500
Schedule of cash, cash equivalents and available-for-sale investments by type of instruments
Cash, Cash equivalents and Short-term investments, Amortized Cost	73,159			77,442
Available-for-sale investments, Gross Unrealized Gains	3,367			8,082
Available-for-sale investments, Gross Unrealized Losses	558			48
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	75,968			85,476
Cash and cash equivalents	27,908		11,992	19,065	[1]	28,065
Short-term investments available-for-sale	48,060			66,411	[1]
Cash [Member]
Schedule of cash, cash equivalents and available-for-sale investments by type of instruments
Cash, Cash equivalents and Short-term investments, Amortized Cost	20,652			8,529
Available-for-sale investments, Gross Unrealized Gains	0			0
Available-for-sale investments, Gross Unrealized Losses	0			0
Cash and Cash equivalents, Estimated Fair Value	20,652			8,529
Cash equivalents [Member]
Schedule of cash, cash equivalents and available-for-sale investments by type of instruments
Cash, Cash equivalents and Short-term investments, Amortized Cost	7,256			10,536
Available-for-sale investments, Gross Unrealized Gains	0			0
Available-for-sale investments, Gross Unrealized Losses	0			0
Cash and Cash equivalents, Estimated Fair Value	7,256			10,536
U.S Treasury securities and agency bonds [Member]
Schedule of cash, cash equivalents and available-for-sale investments by type of instruments
Cash, Cash equivalents and Short-term investments, Amortized Cost	12,400			12,363
Available-for-sale investments, Gross Unrealized Gains	12			10
Available-for-sale investments, Gross Unrealized Losses	2			0
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	12,410			12,373
Corporate bonds [Member]
Schedule of cash, cash equivalents and available-for-sale investments by type of instruments
Cash, Cash equivalents and Short-term investments, Amortized Cost	11,927			15,567
Available-for-sale investments, Gross Unrealized Gains	45			63
Available-for-sale investments, Gross Unrealized Losses	1			2
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	11,971			15,628
Mortgage-backed and asset-backed securities [Member]
Schedule of cash, cash equivalents and available-for-sale investments by type of instruments
Cash, Cash equivalents and Short-term investments, Amortized Cost	4,144			3,655
Available-for-sale investments, Gross Unrealized Gains	339			355
Available-for-sale investments, Gross Unrealized Losses	25			7
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	4,458	[2]		4,003	[2]
Closed-end bond funds [Member]
Schedule of cash, cash equivalents and available-for-sale investments by type of instruments
Cash, Cash equivalents and Short-term investments, Amortized Cost	14,374			21,914
Available-for-sale investments, Gross Unrealized Gains	2,120			5,340
Available-for-sale investments, Gross Unrealized Losses	530			39
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	15,964			27,215
Preferred stock [Member]
Schedule of cash, cash equivalents and available-for-sale investments by type of instruments
Cash, Cash equivalents and Short-term investments, Amortized Cost	2,406			4,878
Available-for-sale investments, Gross Unrealized Gains	851			2,314
Available-for-sale investments, Gross Unrealized Losses	0			0
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	3,257			7,192
Mortgage-backed securities [Member]
Schedule of cash, cash equivalents and available-for-sale investments by type of instruments
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	$ 1,200	[2]		$ 1,400	[2]

[1] Amounts have been derived from the March 31, 2013 audited consolidated financial statements.

[2] At September 30, 2013 and March 31, 2013, approximately $1.2 million and $1.4 million of the estimated fair value presented were mortgage-backed securities, respectively.