Shareholders' Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended	1 Months Ended
	Feb. 28, 2015	Mar. 31, 2015	Dec. 31, 2014	Apr. 30, 2015	Aug. 31, 2011
Shareholder's Equity
Common stock, shares authorized to be repurchased	1,000,000,000
Common stock
Shareholder's Equity
Common stock, shares authorized to be repurchased	20,000,000
Amount of common stock to be repurchased under ASR agreement	$ 300
Shares received under ASR agreement	2,066,293
Common stock, shares reacquired through open and private market purchases		2,946,293	3,547,334
Shares authorized to be repurchased		26,220,005
Number of shares reacquired related to the withholding of taxes for the exercise of stock options and the vesting of stock awards		192,135	489,854
Common stock, shares reacquired		3,138,428
Common stock | Subsequent event
Shareholder's Equity
Shares received under ASR agreement				555,111
Common stock | Nalco
Shareholder's Equity
Additional shares authorized to be repurchased contingent upon merger					10,000,000