Note C - Marketable Equity Securities - Unrealized Gains and Losses on Marketable Securities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Gross unrealized gains	$ 10,287	$ 12,161
Gross unrealized losses	146	109
Net unrealized gains	$ 10,141	$ 12,052