Earnings Per Share (Calculations for EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic and diluted net earnings per share:
Net income attributable to Xylem (in usd)		$ 31	$ 139	$ 69	$ 218
Shares
Weighted average common shares outstanding		179,933	179,964	180,043	179,842
Add: Participating securities	[1]	32	35	29	30
Weighted average common shares outstanding — Basic		179,965	179,999	180,072	179,872
Plus incremental shares from assumed conversions:
Weighted average common shares outstanding — Diluted		180,607	181,153	180,950	181,133
Basic earnings per share (usd per share)		$ 0.17	$ 0.77	$ 0.38	$ 1.21
Diluted earnings per share (usd per share)		$ 0.17	$ 0.77	$ 0.38	$ 1.20
Stock Options
Plus incremental shares from assumed conversions:
Dilutive effect of common shares	[2]	563	832	644	834
Restricted Stock
Plus incremental shares from assumed conversions:
Dilutive effect of common shares	[2]	79	322	234	427

[1] Restricted stock unit awards containing rights to non-forfeitable dividends that participate in undistributed earnings with common shareholders are considered participating securities for purposes of computing earnings per share.

[2] Incremental shares from stock options, restricted stock units and performance share units are computed by the treasury stock method. The weighted average shares listed below were not included in the computation of diluted earnings per share because to do so would have been anti-dilutive for the periods presented or were otherwise excluded under the treasury stock method. The treasury stock method calculates dilution assuming the exercise of all in-the-money options and vesting of restricted stock units and performance share units, reduced by the repurchase of shares with the proceeds from the assumed exercises and unrecognized compensation expense for outstanding awards. Performance share units will be included in the treasury stock calculation of diluted earnings per share upon achievement of underlying performance or market conditions at the end of the reporting period. See Note 15, "Share-Based Compensation Plans", to the condensed consolidated financial statements for further detail on the performance share units.