Equity - Shares and Units and Dividends (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Class of Stock [Line Items]
Percentage of dividends on common stock received until performance criteria met for LTIP units	10.00%		10.00%
Percentage of dividends on common stock received after performance criteria met for LTIP units	90.00%		90.00%
Percentage of dividends on common stock received in periods after performance criteria met for LTIP units	100.00%		100.00%
Net income attributable to common stockholders	$ 11,089	$ 11,120	$ 18,517	$ 14,258
Increase in additional paid-in capital for the conversion of OP Units into common stock			0
Change from net income attributable to common stockholders and transfers from noncontrolling interests	$ 19,432	20,213	$ 33,718	42,844
Shares and Units [Abstract]
OP units outstanding (shares)	269,488,679		269,488,679
OP units owned by the Company (shares)	123,881,223		123,881,223
OP units owned by the Company, percent			46.00%
OP units not owned by the Company (shares)	145,607,456		145,607,456
OP units not owned by the Company, percent			54.00%
Dividends and Distributions [Abstract]
Dividends paid to common shareholders	$ 13,000	9,700	$ 23,300	19,100
Distributions paid to OP unitholders	15,400	13,100	28,000	26,400
Private perpetual preferred unit distributions	200	200	468	468
Additional Paid-In Capital
Class of Stock [Line Items]
Increase in additional paid-in capital for the conversion of OP Units into common stock	$ 8,343	$ 9,093	$ 15,201	$ 28,586