Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Inputs, Level 1 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	$ 6,012	$ 16,274
Fair Value, Inputs, Level 2 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	36,685	29,952
Estimate of Fair Value Measurement [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	42,697	46,226
US Government and Government Agencies and Authorities [Member] | Fair Value, Inputs, Level 2 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	1,000	10,130
US Government and Government Agencies and Authorities [Member] | Estimate of Fair Value Measurement [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	1,000	10,130
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	12,084
US Government Agencies Debt Securities [Member] | Estimate of Fair Value Measurement [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	12,084
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	6,299	5,998
Commercial Paper [Member] | Estimate of Fair Value Measurement [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	6,299	5,998
Certificates of Deposit [Member] | Fair Value, Inputs, Level 2 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	6,000	3,500
Certificates of Deposit [Member] | Estimate of Fair Value Measurement [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	6,000	3,500
Corporate Bond Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	4,012	6,286
Corporate Bond Securities [Member] | Estimate of Fair Value Measurement [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	4,012	6,286
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	6,012	16,274
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	5,115
Money Market Funds [Member] | Estimate of Fair Value Measurement [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	11,127	16,274
Variable Rate Demand Obligation [Member] | Fair Value, Inputs, Level 2 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	2,175	2,785
Variable Rate Demand Obligation [Member] | Estimate of Fair Value Measurement [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value	2,175	2,785
Municipal Notes [Member] | Fair Value, Inputs, Level 2 [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value		1,253
Municipal Notes [Member] | Estimate of Fair Value Measurement [Member]
Note 4 - Current and Non-Current Investments (Details) - Company’s Assets Measured At Fair Value On Recurring Basis [Line Items]
Assets at fair value		$ 1,253