Certain Financial Statement Information (Details 12) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Mar. 31, 2013
Schedule of Gross Unrealized Losses
Less Than 12 Months of Unrealized Losses, Estimated Fair Value	$ 9,502	$ 3,223
Less Than 12 Months of Unrealized Losses, Gross Unrealized Losses	(476)	(5)
12 Months or More of Unrealized Losses, Estimated Fair Value	403	7,104
12 Months or More of Unrealized Losses, Gross Unrealized Losses	(82)	(43)
Total, Estimated Fair Value	9,905	10,327
Total, Gross Unrealized Losses	(558)	(48)
Gross unrealized gains	3,367	8,082
U.S Treasury securities and agency bonds [Member]
Schedule of Gross Unrealized Losses
Less Than 12 Months of Unrealized Losses, Estimated Fair Value	1,468	300
Less Than 12 Months of Unrealized Losses, Gross Unrealized Losses	(2)	0
12 Months or More of Unrealized Losses, Estimated Fair Value	0	0
12 Months or More of Unrealized Losses, Gross Unrealized Losses	0	0
Total, Estimated Fair Value	1,468	300
Total, Gross Unrealized Losses	(2)	0
Gross unrealized gains	12	10
Corporate bonds [Member]
Schedule of Gross Unrealized Losses
Less Than 12 Months of Unrealized Losses, Estimated Fair Value	1,654	2,276
Less Than 12 Months of Unrealized Losses, Gross Unrealized Losses	(1)	(2)
12 Months or More of Unrealized Losses, Estimated Fair Value	0	113
12 Months or More of Unrealized Losses, Gross Unrealized Losses	0	0
Total, Estimated Fair Value	1,654	2,389
Total, Gross Unrealized Losses	(1)	(2)
Gross unrealized gains	45	63
Mortgage-backed and asset-backed securities [Member]
Schedule of Gross Unrealized Losses
Less Than 12 Months of Unrealized Losses, Estimated Fair Value	1,675	647
Less Than 12 Months of Unrealized Losses, Gross Unrealized Losses	(25)	(3)
12 Months or More of Unrealized Losses, Estimated Fair Value	12	0
12 Months or More of Unrealized Losses, Gross Unrealized Losses	0	(4)
Total, Estimated Fair Value	1,687	647
Total, Gross Unrealized Losses	(25)	(7)
Gross unrealized gains	339	355
Closed-end bond funds [Member]
Schedule of Gross Unrealized Losses
Less Than 12 Months of Unrealized Losses, Estimated Fair Value	4,705	0
Less Than 12 Months of Unrealized Losses, Gross Unrealized Losses	(448)	0
12 Months or More of Unrealized Losses, Estimated Fair Value	391	6,991
12 Months or More of Unrealized Losses, Gross Unrealized Losses	(82)	(39)
Total, Estimated Fair Value	5,096	6,991
Total, Gross Unrealized Losses	(530)	(39)
Gross unrealized gains	$ 2,120	$ 5,340