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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income available for Common Stockholders	$ 46,401	$ 46,137	$ 159,710	$ 106,359
Amounts allocated to dilutive securities	2,676	3,024	9,902	6,979
Net income available for Common Stockholders – Fully Diluted	$ 49,077	$ 49,161	$ 169,612	$ 113,338
Denominator:
Weighted average Common Shares outstanding – basic (shares)	90,156	88,549	89,969	88,537
Effect of dilutive securities:
Exchange of Common OP Units for Common Shares (shares)	5,643	5,826	5,691	5,827
Restricted stock and options (shares)	131	248	113	236
Weighted average Common Shares outstanding – Fully Diluted (shares)	95,930	94,623	95,773	94,600
Earnings per Common Share – Basic (usd per share)	$ 0.51	$ 0.52	$ 1.78	$ 1.20
Earnings per Common Share – Fully Diluted (usd per share)	$ 0.51	$ 0.52	$ 1.77	$ 1.20