Note 10 - Fair Value Measurements (Details) - Financial Assets and Liabilities, Fair Value - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Assets	$ 193,048	$ 180,155
Liabilities:
Contingent consideration	2,507	2,507
Total	2,507	2,507
Money Market Funds [Member]
Assets:
Assets	31,135	60,078
Certificates of Deposit [Member]
Assets:
Assets	22,008	22,778
US Government Agencies Short-term Debt Securities [Member]
Assets:
Assets	131,039	89,674
Auction Rate Securities [Member]
Assets:
Assets	5,364	5,389
Equity Funds [Member]
Assets:
Assets	3,502	2,236
Fair Value, Inputs, Level 1 [Member]
Assets:
Assets	34,637	62,314
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Assets:
Assets	31,135	60,078
Fair Value, Inputs, Level 1 [Member] | Equity Funds [Member]
Assets:
Assets	3,502	2,236
Fair Value, Inputs, Level 2 [Member]
Assets:
Assets	153,047	112,452
Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member]
Assets:
Assets	22,008	22,778
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Short-term Debt Securities [Member]
Assets:
Assets	131,039	89,674
Fair Value, Inputs, Level 3 [Member]
Assets:
Assets	5,364	5,389
Liabilities:
Contingent consideration	2,507	2,507
Total	2,507	2,507
Fair Value, Inputs, Level 3 [Member] | Auction Rate Securities [Member]
Assets:
Assets	$ 5,364	$ 5,389