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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income available for Common Stockholders	$ 64,461	$ 56,070	$ 224,171	$ 162,429
Amounts allocated to dilutive securities	3,715	3,590	13,617	10,569
Net income available for Common Stockholders – Fully Diluted	$ 68,176	$ 59,660	$ 237,788	$ 172,998
Denominator:
Weighted average Common Shares outstanding – basic (shares)	181,649	178,400	180,515	177,520
Effect of dilutive securities:
Exchange of Common OP Units for Common Shares (shares)	10,496	11,542	11,084	11,618
Restricted stock and options (shares)	255	584	241	516
Weighted average Common Shares outstanding – Fully Diluted (shares)	192,400	190,526	191,840	189,654
Earnings per Common Share – Basic (usd per share)	$ 0.35	$ 0.31	$ 1.24	$ 0.91
Earnings per Common Share – Fully Diluted (usd per share)	$ 0.35	$ 0.31	$ 1.24	$ 0.91