Earnings Per Common Share - Computation of Basic and Diluted Net Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Weighted average number of common shares outstanding - basic (in shares)	73,461	72,839	73,272	72,718
Effect of dilutive securities (in shares)	1,077	753	980	717
Weighted average number of common shares outstanding - diluted (in shares)	74,538	73,592	74,252	73,435