Stockholders' Equity - Computation of basic and diluted earnings (loss) per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Weighted average Common Shares outstanding
Weighted average common shares outstanding (in shares)	145,594,127	136,048,781	143,305,737	135,393,798
Non-vested shares (in shares)	(1,776,508)	(1,739,364)	(1,784,544)	(1,731,658)
Weighted average common shares outstanding - basic (in shares)	143,817,619	134,309,417	141,521,193	133,662,140
Dilutive effect of forward equity shares (in shares)	0	0	14,036	0
Dilutive effect of employee stock purchase plan (in shares)	0	47,810	78,200	74,029
Weighted average common shares outstanding - diluted (in shares)	143,817,619	134,357,227	141,613,429	133,736,169
Net Income (loss)	$ (2,066)	$ 8,230	$ 45,052	$ 88,058
Dividends paid on nonvested share-based awards	(537)	(522)	(1,617)	(1,561)
Net income (loss) applicable to common stockholders	$ (2,603)	$ 7,708	$ 43,435	$ 86,497
Basic earnings per common share (in dollars per share)	$ (0.02)	$ 0.06	$ 0.31	$ 0.65
Diluted earnings per common share (in dollars per share)	$ (0.02)	$ 0.06	$ 0.31	$ 0.65