Certain Financial Statement Information - Short Term Investments Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Mar. 31, 2016
Cash
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	$ 21,449	$ 23,510
Money Market Funds [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	1,040	1,555
U.S. Treasury and agency securities
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	16,255	14,898
Corporate bonds
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	25,539	28,263
Asset-backed and mortgage-backed securities
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	16,634	13,551
Municipal bonds
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	811	2,068
Recurring
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	81,728	83,845
Recurring | Level 1
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	38,744	39,963
Recurring | Level 2
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	42,984	43,882
Recurring | Level 3
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	0	0
Recurring | Cash
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	21,449	23,510
Recurring | Cash | Level 1
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	21,449	23,510
Recurring | Cash | Level 2
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	0	0
Recurring | Cash | Level 3
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	0	0
Recurring | Money Market Funds [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	1,040	1,555
Recurring | Money Market Funds [Member] | Level 1
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	1,040	1,555
Recurring | Money Market Funds [Member] | Level 2
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	0	0
Recurring | Money Market Funds [Member] | Level 3
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	0	0
Recurring | U.S. Treasury and agency securities
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	16,255	14,898
Recurring | U.S. Treasury and agency securities | Level 1
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	16,255	14,898
Recurring | U.S. Treasury and agency securities | Level 2
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	0	0
Recurring | U.S. Treasury and agency securities | Level 3
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	0	0
Recurring | Corporate bonds
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	25,539	28,263
Recurring | Corporate bonds | Level 1
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	0	0
Recurring | Corporate bonds | Level 2
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	25,539	28,263
Recurring | Corporate bonds | Level 3
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	0	0
Recurring | Asset-backed and mortgage-backed securities
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	16,634	13,551
Recurring | Asset-backed and mortgage-backed securities | Level 1
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	0	0
Recurring | Asset-backed and mortgage-backed securities | Level 2
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	16,634	13,551
Recurring | Asset-backed and mortgage-backed securities | Level 3
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	0	0
Recurring | Municipal bonds
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	811	2,068
Recurring | Municipal bonds | Level 1
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	0	0
Recurring | Municipal bonds | Level 2
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	811	2,068
Recurring | Municipal bonds | Level 3
Schedule of Cash, Cash Equivalents and Available-For-Sale Investments by Type of Instruments Measured at Fair Value on Recurring Basis
Available-for-sale securities	$ 0	$ 0