Stockholders' Equity - Reconciliation of Weighted Average Shares (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income:
Net income	$ 16,609	$ 15,504	$ 11,857	$ 9,087	$ 10,023	$ 10,624	$ 11,828	$ 9,316	$ 53,057	$ 41,791	$ 38,918
Dividends and undistributed earnings allocated to participating securities									(321)	(293)	(358)
Net income allocated to common shareholders									$ 52,736	$ 41,498	$ 38,560
Basic:
Weighted average common shares outstanding (in shares)									35,281,408	29,937,400	29,963,365
Restricted stock awards (in shares)									(87,405)	(179,581)	(285,063)
Total basic weighted average common shares outstanding (in shares)									35,194,003	29,757,819	29,678,302
Diluted:
Basic weighted average common shares outstanding (in shares)									35,194,003	29,757,819	29,678,302
Effect of potentially dilutive common shares (in shares)									177,587	91,512	13,851
Total diluted weighted average common shares outstanding (in shares)									35,371,590	29,849,331	29,692,153