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
	Mar. 31, 2016	Mar. 31, 2015
Numerators:
Net income available for Common Stockholders	$ 50,583	$ 27,185
Amounts allocated to dilutive securities	4,310	2,331
Net income available for Common Stockholders – fully diluted	$ 54,893	$ 29,516
Denominator:
Weighted average Common Shares outstanding – basic (shares)	84,321	83,961
Effect of dilutive securities:
Redemption of Common OP Units for Common Shares (shares)	7,208	7,225
Stock options and restricted shares (shares)	512	591
Weighted average Common Shares outstanding – fully diluted (shares)	92,041	91,777
Earnings per Common Share – Basic:
Net income available for Common Shares (usd per share)	$ 0.60	$ 0.32
Earnings per Common Share – Fully Diluted:
Net income available for Common Shares (usd per share)	$ 0.60	$ 0.32