CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Jun. 30, 2013	Dec. 31, 2012
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)	256,630,645	255,592,901
Common stock voting, shares outstanding (in shares)	220,665,831	219,522,655
Treasury stock, shares (in shares)	35,964,814	36,070,246