Earnings per Share (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 20,619	$ 13,786	$ 37,384	$ 41,427
Weighted average basic shares outstanding (in shares)	31,703,000	31,579,000	31,700,000	31,493,000
Common stock options and restricted stock (in shares)	507,000	597,000	516,000	512,000
Weighted average shares outstanding, diluted (in shares)	32,210,000	32,176,000	32,216,000	32,005,000
Common shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share calculation (in shares)	489,000	621,000	523,000	690,000