Stockholders' Equity - Reconciliation of Denominators used in Computation of Basic and Diluted Earnings Per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Stockholders' Equity Note [Abstract]
Basic weighted average shares outstanding (in shares)	287,140,426	288,655,020	287,391,614	288,948,734
Weighted shares assumed upon exercise of stock options (in shares)	117,061	133,943	167,854	150,582
Diluted weighted average shares outstanding (in shares)	287,257,487	288,788,963	287,559,468	289,099,316