CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Sep. 30, 2012	Dec. 31, 2011
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)	255,299,134	255,052,811
Common stock voting, shares outstanding (in shares)	219,228,888	218,873,720
Treasury stock, shares (in shares)	36,070,246	36,179,091
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%
6 1/8% senior notes, due 2019
Long-term debt
Note stated interest rate (as a percent)	6.125%
7 5/8% senior notes, due 2020
Long-term debt
Note stated interest rate (as a percent)	7.625%	7.625%
6 3/8% Senior Notes, due 2022
Long-term debt
Note stated interest rate (as a percent)	6.375%