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Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive securities (in shares)							28,000	21,000
Net income	$ 13,448	$ 12,848	$ 15,926	$ 18,564	$ 21,895	$ 13,646	$ 42,222	$ 54,105
Weighted average number of shares outstanding- basic (shares)	34,688,206			36,732,746			34,911,640	37,012,536
Effect of dilutive securities:
Total effect of dilutive securities (shares)	87,245			186,158			85,054	168,851
Weighted average number of shares outstanding - diluted (shares)	34,775,451			36,918,904			34,996,694	37,181,387
Basic earnings per share (usd per share)	$ 0.39			$ 0.51			$ 1.21	$ 1.46
Diluted earnings per share (usd per share)	$ 0.39			$ 0.50			$ 1.21	$ 1.46
Restricted stock awards
Effect of dilutive securities:
Effect of dilutive securities (shares)	0			0			0	1,170
Restricted stock units
Effect of dilutive securities:
Effect of dilutive securities (shares)	37,656			89,750			37,308	72,650
Performance-based restricted stock units
Effect of dilutive securities:
Effect of dilutive securities (shares)	33,809			68,384			31,679	67,231
Stock options
Effect of dilutive securities:
Effect of dilutive securities (shares)	15,780			28,024			16,067	27,800