Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Stockholders' deficiency:
Long-term investments, fair value	$ 52,384	$ 54,628
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	147,790,061	140,914,642
Common stock, shares outstanding (in shares)	147,790,061	140,914,642