Earnings Per Common Share - Computation of Basic and Diluted Net Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net income	$ 18,626	$ 15,516
Basic earnings per common share, Income (Numerator)	$ 18,626	$ 15,516
Basic earnings per common share, Shares (Denominator) (in shares)	72,364	71,469
Basic earnings per common share, Per-share Amount (in dollars per share)	$ 0.26	$ 0.22
Effect of dilutive securities:
Stock options and restricted stock, Shares (Denominator) (in shares)	650	690
Stock options and restricted stock, Per-share Amount (in dollars per share)	$ 0.00	$ 0.00
Diluted earnings per common share, Income (Numerator)	$ 18,626	$ 15,516
Diluted earnings per common share, Shares (Denominator) (in shares)	73,014	72,159
Diluted earnings per common share, Per-share Amount (in dollars per share)	$ 0.26	$ 0.22