CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 6 3/4% senior notes, due 2015	Dec. 31, 2011 6 3/4% senior notes, due 2015	Jun. 30, 2012 7 5/8% senior notes, due 2020	Dec. 31, 2011 7 5/8% senior notes, due 2020
Common stock voting, par value (in dollars per share)	$ 0.0025	$ 0.0025
Common stock voting, shares authorized (in shares)	900,000,000	900,000,000
Common stock voting, shares issued (in shares)	255,225,325	255,052,811
Common stock voting, shares outstanding (in shares)	219,154,966	218,873,720
Treasury stock, shares (in shares)	36,070,359	36,179,091
Long-term debt
Note stated interest rate (as a percent)			6.75%	6.75%	7.625%	7.625%