Investments - Summary by Type of Instruments Measured at Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	$ 85,476		$ 113,846
Cash, cash equivalents and available-for-sale investments measured at fair value on recurring basis	85,476		113,846
Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and available-for-sale investments measured at fair value on recurring basis	57,625		72,243
Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and available-for-sale investments measured at fair value on recurring basis	27,851		41,603
Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and available-for-sale investments measured at fair value on recurring basis	0		0
Cash [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents measured at fair value on a recurring basis	8,529		15,057
Cash [Member] | Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents measured at fair value on a recurring basis	8,529		15,057
Cash [Member] | Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents measured at fair value on a recurring basis			0
Cash [Member] | Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents measured at fair value on a recurring basis	0		0
Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents measured at fair value on a recurring basis	10,536		13,008
Cash Equivalents [Member] | Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents measured at fair value on a recurring basis	9,508		10,510
Cash Equivalents [Member] | Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents measured at fair value on a recurring basis	1,028		2,498
Cash Equivalents [Member] | Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents measured at fair value on a recurring basis	0		0
U.S Treasury securities and agency bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	12,373		16,763
U.S Treasury securities and agency bonds [Member] | Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	12,373		16,763
U.S Treasury securities and agency bonds [Member] | Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis			0
U.S Treasury securities and agency bonds [Member] | Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	15,628		23,407
Corporate bonds [Member] | Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis			0
Corporate bonds [Member] | Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	15,628		23,407
Corporate bonds [Member] | Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
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 Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	4,003	[1]	7,611	[1]
Mortgage-backed and asset-backed securities [Member] | Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis			0
Mortgage-backed and asset-backed securities [Member] | Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	4,003		7,611
Mortgage-backed and asset-backed securities [Member] | Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Closed-end bond funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	27,215		29,913
Closed-end bond funds [Member] | Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	27,215		29,913
Closed-end bond funds [Member] | Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis			0
Closed-end bond funds [Member] | Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	0		0
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	7,192		8,087
Preferred Stock [Member] | Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis			0
Preferred Stock [Member] | Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	7,192		8,087
Preferred Stock [Member] | Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, cash equivalents and short term investments, measured at fair value on a recurring basis	$ 0		$ 0

[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.