STOCKHOLDERS' EQUITY (Schedule of Stock by Class) (Details) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Stockholders’ equity:
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	73,121,229	71,185,468
Undesignated preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Undesignated preferred stock, shares issued (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.000001	$ 0.000001