Certain Financial Statement Information (Details 9) (USD $)	3 Months Ended
	Jun. 30, 2013		Jun. 30, 2012	Mar. 31, 2013		Dec. 31, 2012	Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Percentage of voting interest						20.00%
Investments in non-marketable equity investments, cost method	$ 0		$ 500,000
Schedule of cash, cash equivalents and available-for-sale investments by type of instruments
Cash, Cash equivalents and Short-term investments, Amortized Cost	86,225,000			77,442,000
Available-for-sale investments, Gross Unrealized Gains	4,084,000			8,082,000
Available-for-sale investments, Gross Unrealized Losses	579,000			48,000
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	89,730,000			85,476,000
Cash and cash equivalents	39,673,000		20,714,000	19,065,000	[1]		28,065,000
Short-term investments available-for-sale	50,057,000			66,411,000	[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	13,140,000			8,529,000
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	13,140,000			8,529,000
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	26,533,000			10,536,000
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	26,533,000			10,536,000
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	12,521,000			12,363,000
Available-for-sale investments, Gross Unrealized Gains	6,000			10,000
Available-for-sale investments, Gross Unrealized Losses	12,000			0
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	12,515,000			12,373,000
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	10,800,000			15,567,000
Available-for-sale investments, Gross Unrealized Gains	38,000			63,000
Available-for-sale investments, Gross Unrealized Losses	9,000			2,000
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	10,829,000			15,628,000
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	4,130,000			3,655,000
Available-for-sale investments, Gross Unrealized Gains	362,000			355,000
Available-for-sale investments, Gross Unrealized Losses	20,000			7,000
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	4,472,000	[2]		4,003,000	[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	16,695,000			21,914,000
Available-for-sale investments, Gross Unrealized Gains	2,754,000			5,340,000
Available-for-sale investments, Gross Unrealized Losses	538,000			39,000
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	18,911,000			27,215,000
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	2,406,000			4,878,000
Available-for-sale investments, Gross Unrealized Gains	924,000			2,314,000
Available-for-sale investments, Gross Unrealized Losses	0			0
Cash, Cash equivalents and Short-term investments, Estimated Fair Value	3,330,000			7,192,000
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	$ 1,300,000	[2]		$ 1,400,000	[2]

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

[2] At June 30, 2013 and March 31, 2013, approximately $1.3 million and $1.4 million of the estimated fair value presented were mortgage-backed securities, respectively.