CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Stockholders' equity:
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	20,000,000	20,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0013	$ 0.0013
Common stock, authorized (in shares)	160,000,000	160,000,000
Common stock, issued (in shares)	70,146,317	69,832,949
Treasury stock, shares (in shares)	200,000	200,000