CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Convertible senior notes, interest rate	3.625%
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized	10,000,000	10,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, authorized	450,000,000	450,000,000
Common stock, shares issued	186,862,477	185,896,080
Common stock, shares outstanding	186,862,477	185,896,080