Net Income Per Common Share (Narrative) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 19, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares	1,700,000	2,200,000	2,200,000
Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Exercise price (in dollars per share)				$ 65.52
Common Stock | Maximum
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Maximum repurchase amount (in shares)				2,200,000.0