CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2016	Dec. 31, 2015
CONSOLIDATED BALANCE SHEETS
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)	263,142,777	262,937,139
Common stock voting, shares outstanding (in shares)	243,500,764	243,089,514
Treasury stock, shares (in shares)	19,642,013	19,847,625