Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted Average Number of Shares Outstanding Basic and Diluted [Line Items]
Common stock, shares, outstanding	102,748,700	106,684,084	107,906,644
Repurchased and retired common stock	5,993,959	3,267,881
Treasury Stock, Shares, Acquired	600,000	700,000	700,000
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted-average number of common shares outstanding - basic	104,800,000	108,100,000	107,000,000
Adjusted weighted average shares and assumed conversions - diluted	107,000,000	110,900,000	109,200,000
Potentially dilutive shares excluded from computation of dilutive earnings per share	4,000,000	3,100,000	3,600,000
Stock options
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Incremental common shares attributable to share-based payment arrangements	1,000,000	1,300,000	800,000
Restricted stock units
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Incremental common shares attributable to share-based payment arrangements	1,200,000	1,500,000	1,400,000