Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Short-term investments, amortized cost	$ 133,744
Allowance	$ 863	$ 1,314
Preferred stock designated Series A, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock designated Series A, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock designated Series A, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	288,923,000	286,877,000
Common stock, shares outstanding (in shares)	242,829,000	240,805,000
Treasury stock (in shares)	46,094,000	46,072,000
Property, plant and equipment, net	$ 2,566,002	$ 2,404,850