CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Jun. 30, 2011	Dec. 31, 2010
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)	254,987,769	254,002,799
Common stock voting, shares outstanding (in shares)	218,648,678	217,574,826
Treasury stock, shares (in shares)	36,339,091	36,427,973
7 3/8% senior notes, due 2012
Long-term debt
Note stated interest rate (as a percent)	7.375%	7.375%
5.125% convertible senior notes, due 2014
Long-term debt
Note stated interest rate (as a percent)	5.125%	5.125%
6 3/4% senior notes, due 2015
Long-term debt
Note stated interest rate (as a percent)	6.75%	6.75%
7 3/4% senior notes, due 2016
Long-term debt
Note stated interest rate (as a percent)	7.75%	7.75%
7 5/8% senior notes, due 2020
Long-term debt
Note stated interest rate (as a percent)	7.625%	7.625%