Earnings per Share (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 12,769	$ 18,612	$ 16,765	$ 27,641
Weighted average basic shares outstanding (in shares)	31,709,000	31,475,000	31,698,000	31,447,000
Common stock options and restricted stock (in shares)	474,000	532,000	521,000	469,000
Weighted average shares outstanding, diluted (in shares)	32,183,000	32,007,000	32,219,000	31,916,000
Common shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share calculation (in shares)	556,000	764,000	541,000	724,000