Stockholders' Equity - Computation of basic and diluted earnings (loss) per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Weighted average Common Shares outstanding
Weighted average common shares outstanding (in shares)	143,700,491	135,367,081	142,142,577	135,062,708
Non-vested shares (in shares)	(1,783,278)	(1,733,435)	(1,788,410)	(1,727,762)
Weighted average common shares outstanding - basic (in shares)	141,917,213	133,633,646	140,354,167	133,334,946
Dilutive effect of forward equity shares (in shares)	61,064	0	27,896	2,149
Dilutive effect of employee stock purchase plan (in shares)	70,711	62,266	85,714	83,217
Weighted average common shares outstanding - diluted (in shares)	142,048,988	133,695,912	140,467,777	133,420,312
Net Income	$ 23,096	$ 75,513	$ 47,118	$ 79,828
Dividends paid on nonvested share-based awards	(539)	(521)	(1,080)	(1,039)
Net income applicable to common stockholders	$ 22,557	$ 74,992	$ 46,038	$ 78,789
Basic earnings per common share (in dollars per share)	$ 0.16	$ 0.56	$ 0.33	$ 0.59
Diluted earnings per common share (in dollars per share)	$ 0.16	$ 0.56	$ 0.33	$ 0.59