Earnings Per Common Share - Calculation of numerator and denominator in eps table (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerators:
Net income available for common stockholders	$ 50,560	$ 64,461	$ 163,622	$ 224,171
Amounts allocated to dilutive securities	2,908	3,715	9,415	13,617
Net income available for common stockholders – fully diluted	$ 53,468	$ 68,176	$ 173,037	$ 237,788
Denominators:
Weighted average common shares outstanding – basic (in shares)	181,869	181,649	181,811	180,515
Effect of dilutive securities:
Exchange of common OP units for common shares (in shares)	10,482	10,496	10,485	11,084
Restricted stock and options (in shares)	186	255	252	241
Weighted average common shares outstanding – fully diluted (in shares)	192,537	192,400	192,548	191,840
Earnings per common share – basic (usd per share)	$ 0.28	$ 0.35	$ 0.90	$ 1.24
Earnings per common share – fully diluted (usd per share)	$ 0.28	$ 0.35	$ 0.90	$ 1.24