Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income	$ 18,241	$ 23,810	$ 26,492	$ 30,359
Less: Dividends declared on unvested time-based awards	(119)	(119)	(237)	(240)
Less: Undistributed earnings allocated to unvested time-based awards	0	0	0	0
Net income available to common shareholders, excluding amounts attributable to unvested time-based awards	$ 18,122	$ 23,691	$ 26,255	$ 30,119
Denominator:
Weighted-average number of common shares outstanding - basic	59,394,134	59,133,648	59,392,327	59,126,894
Effect of dilutive unvested performance-based awards	867,669	659,415	848,937	633,871
Weighted-average number of shares outstanding - diluted	60,261,803	59,793,063	60,241,264	59,760,765
Net income available per common share - basic	$ 0.31	$ 0.40	$ 0.44	$ 0.51
Net income available per common share - diluted	$ 0.30	$ 0.40	$ 0.44	$ 0.50
Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of earnings per share, amount	0	107,559	0	107,559