Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2018

Summary of Significant Accounting Policies

Reconciliation of basic weighted average shares outstanding to diluted weighted average shares outstanding

	Three Months Ended March 31,
	2017	2018
Basic weighted average number of shares outstanding	314,954	316,471
Add: Dilutive effect of restricted stock units	770	401
Add: Dilutive effect of outstanding stock options	—	—
Add: Dilutive effect of performance stock units	45	39
Diluted weighted average number of shares outstanding	315,769	316,911
Weighted average number of outstanding equity awards excluded from calculation of diluted earnings per common share(1):
Restricted stock units	1,509	421
Outstanding stock options	683	653
Performance stock units	660	1,189

(1)   The potential dilutive effects of these awards were excluded from the computation of earnings per common share—assuming dilution because the inclusion of these awards would have been anti-dilutive.