Certain Financial Statement Information (Details 10) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Mar. 31, 2012
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	$ 84,244		$ 113,846
Cash, cash equivalents and available-for-sale investments measured at fair value on recurring basis	84,244		113,846
Level 1 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and available-for-sale investments measured at fair value on recurring basis	54,628		72,243
Level 2 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and available-for-sale investments measured at fair value on recurring basis	29,616		41,603
Level 3 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and available-for-sale investments measured at fair value on recurring basis	0		0
Cash [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash and cash equivalents measured at fair value on a recurring basis	8,683		15,057
Cash [Member] | Level 1 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash and cash equivalents measured at fair value on a recurring basis	8,683		15,057
Cash [Member] | Level 2 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash and cash equivalents measured at fair value on a recurring basis	0		0
Cash [Member] | Level 3 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash and cash equivalents measured at fair value on a recurring basis	0		0
Cash equivalents [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash and cash equivalents measured at fair value on a recurring basis	7,000		13,008
Cash equivalents [Member] | Level 1 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash and cash equivalents measured at fair value on a recurring basis	7,000		10,510
Cash equivalents [Member] | Level 2 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash and cash equivalents measured at fair value on a recurring basis	0		2,498
Cash equivalents [Member] | Level 3 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash and cash equivalents measured at fair value on a recurring basis	0		0
U.S Treasury securities and agency bonds [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	12,154		16,763
U.S Treasury securities and agency bonds [Member] | Level 1 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	12,154		16,763
U.S Treasury securities and agency bonds [Member] | Level 2 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
U.S Treasury securities and agency bonds [Member] | Level 3 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Corporate bonds [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	18,435		23,407
Corporate bonds [Member] | Level 1 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Corporate bonds [Member] | Level 2 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	18,435		23,407
Corporate bonds [Member] | Level 3 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Mortgage-backed and asset-backed securities [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	4,416	[1]	7,611	[1]
Mortgage-backed and asset-backed securities [Member] | Level 1 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Mortgage-backed and asset-backed securities [Member] | Level 2 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	4,416		7,611
Mortgage-backed and asset-backed securities [Member] | Level 3 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Closed-end bond funds [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	26,791		29,913
Closed-end bond funds [Member] | Level 1 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	26,791		29,913
Closed-end bond funds [Member] | Level 2 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Closed-end bond funds [Member] | Level 3 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Preferred stock [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	6,765		8,087
Preferred stock [Member] | Level 1 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Preferred stock [Member] | Level 2 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	6,765		8,087
Preferred stock [Member] | Level 3 [Member]
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	$ 0		$ 0

[1] At December 31, 2012 and March 31, 2012, approximately $1.7 million and $4.6 million of the estimated fair value presented were mortgage-backed securities, respectively.