Earnings Per Common Share - Calculation of basic and diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income	$ 20,662	$ (10,054)	$ 19,698	$ 16,053	$ 15,539	$ 14,510	$ 13,267	$ 14,607	$ 46,359	$ 57,923	$ 25,874
Less: Net income allocated to participating securities									(296)	(364)	(354)
Numerator for basic and diluted earnings available to common stockholders									$ 46,063	$ 57,559	$ 25,520
Denominator:
Weighted-average basic common shares outstanding (shares)	95,103	95,103	94,036	88,010	84,059	81,490	76,374	75,504	93,088	79,386	72,647
Weighted-average diluted common shares outstanding (shares)	95,144	95,103	94,036	88,010	84,084	81,490	76,374	75,504	93,098	79,392	72,647
Earnings per common share, basic (usd per share)	$ 0.22	$ (0.11)	$ 0.21	$ 0.18	$ 0.18	$ 0.18	$ 0.17	$ 0.19	$ 0.49	$ 0.73	$ 0.35
Earnings per common share, diluted (usd per share)	$ 0.22	$ (0.11)	$ 0.21	$ 0.18	$ 0.18	$ 0.18	$ 0.17	$ 0.19	$ 0.49	$ 0.72	$ 0.35