Supplemental Balance Sheet, Income Statement and Cash Flow Information (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investment income (loss)
Interest and dividend income	$ 1,850	$ 6,267	$ 5,120
Gains (losses) on investments, net	458	5,564	91,457
Investment income (loss)	2,308	$ 11,831	$ 96,577
Net unrealized gains (loss) from trading securities	2,500
Realized gains on available-for-sale securities	$ 89,000