Certain Financial Statement Information (Details 12) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Mar. 31, 2012
Schedule of Gross Unrealized Losses
Less Than 12 Months of Unrealized Losses, Estimated Fair Value	$ 5,704	$ 15,295
Less Than 12 Months of Unrealized Losses, Gross Unrealized Losses	(12)	(49)
12 Months or More of Unrealized Losses, Estimated Fair Value	7,211	6,981
12 Months or More of Unrealized Losses, Gross Unrealized Losses	(1,232)	(1,690)
Total, Estimated Fair Value	12,915	22,276
Total, Gross Unrealized Losses	(1,244)	(1,739)
U.S Treasury securities and agency bonds [Member]
Schedule of Gross Unrealized Losses
Less Than 12 Months of Unrealized Losses, Estimated Fair Value	2,131	8,938
Less Than 12 Months of Unrealized Losses, Gross Unrealized Losses	(2)	(19)
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	2,131	8,938
Total, Gross Unrealized Losses	(2)	(19)
Corporate bonds [Member]
Schedule of Gross Unrealized Losses
Less Than 12 Months of Unrealized Losses, Estimated Fair Value	2,950	5,463
Less Than 12 Months of Unrealized Losses, Gross Unrealized Losses	(3)	(10)
12 Months or More of Unrealized Losses, Estimated Fair Value	245	0
12 Months or More of Unrealized Losses, Gross Unrealized Losses	(5)	0
Total, Estimated Fair Value	3,195	5,463
Total, Gross Unrealized Losses	(8)	(10)
Mortgage-backed and asset-backed securities [Member]
Schedule of Gross Unrealized Losses
Less Than 12 Months of Unrealized Losses, Estimated Fair Value	580	894
Less Than 12 Months of Unrealized Losses, Gross Unrealized Losses	(5)	(20)
12 Months or More of Unrealized Losses, Estimated Fair Value	16	353
12 Months or More of Unrealized Losses, Gross Unrealized Losses	(4)	(41)
Total, Estimated Fair Value	596	1,247
Total, Gross Unrealized Losses	(9)	(61)
Closed-end bond funds [Member]
Schedule of Gross Unrealized Losses
Less Than 12 Months of Unrealized Losses, Estimated Fair Value	43	0
Less Than 12 Months of Unrealized Losses, Gross Unrealized Losses	(2)	0
12 Months or More of Unrealized Losses, Estimated Fair Value	6,950	6,628
12 Months or More of Unrealized Losses, Gross Unrealized Losses	(1,223)	(1,649)
Total, Estimated Fair Value	6,993	6,628
Total, Gross Unrealized Losses	$ (1,225)	$ (1,649)