Investments - Summary of Available-for-Sale Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Mar. 31, 2012		Mar. 31, 2011	Mar. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Cash, Cash equivalents and Short-term investments, Amortized Cost	$ 77,442		$ 108,115
Available-for-sale investments, Gross Unrealized Gains	8,082		7,470
Available-for-sale investments, Gross Unrealized Losses	48		1,739
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	85,476		113,846
Cash and cash equivalents	19,065		28,065		84,402	122,526
Short-term investments available-for-sale	66,411		85,781
Cash [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, Cash equivalents and Short-term investments, Amortized Cost	8,529		15,057
Available-for-sale investments, Gross Unrealized Gains	0		0
Available-for-sale investments, Gross Unrealized Losses	0		0
Cash and cash equivalents measured at fair value on a recurring basis	8,529		15,057
Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, Cash equivalents and Short-term investments, Amortized Cost	10,536		13,008
Available-for-sale investments, Gross Unrealized Gains	0		0
Available-for-sale investments, Gross Unrealized Losses	0		0
Cash and cash equivalents measured at fair value on a recurring basis	10,536		13,008
U.S Treasury Securities and Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, Cash equivalents and Short-term investments, Amortized Cost	12,363		16,771
Available-for-sale investments, Gross Unrealized Gains	10		11
Available-for-sale investments, Gross Unrealized Losses	0		19
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	12,373		16,763
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, Cash equivalents and Short-term investments, Amortized Cost	15,567		23,361
Available-for-sale investments, Gross Unrealized Gains	63		56
Available-for-sale investments, Gross Unrealized Losses	2		10
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	15,628		23,407
Mortgage Backed and Asset Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, Cash equivalents and Short-term investments, Amortized Cost	3,655	[1]	7,308	[1]
Available-for-sale investments, Gross Unrealized Gains	355	[1]	364	[1]
Available-for-sale investments, Gross Unrealized Losses	7	[1]	61	[1]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	4,003	[1]	7,611	[1]
Closed-end bond funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, Cash equivalents and Short-term investments, Amortized Cost	21,914		26,401
Available-for-sale investments, Gross Unrealized Gains	5,340		5,161
Available-for-sale investments, Gross Unrealized Losses	39		1,649
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	27,215		29,913
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, Cash equivalents and Short-term investments, Amortized Cost	4,878		6,209
Available-for-sale investments, Gross Unrealized Gains	2,314		1,878
Available-for-sale investments, Gross Unrealized Losses	0		0
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	$ 7,192		$ 8,087

[1] At March 31, 2013 and 2012, approximately $1.4 million and $4.6 million of the estimated fair value presented were mortgage-backed securities, respectively.