Earnings per Share and Unit (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share Basic [Line Items]
Weighted average common shares/units outstanding for basic EPS/EPU										169,231,000	167,526,000	169,724,000
Weighted average common shares/units outstanding for diluted EPS/EPU	[1]									169,460,000	167,771,000	170,100,000
Income per common share - basic		$ 0.23	$ 0.07	$ 0.11	$ (0.15)	$ 0.24	$ 0.34	$ 0.31	$ 0.54	$ 0.27	$ 1.43	$ 1.47
Income per common share - diluted		$ 0.23	$ 0.07	$ 0.11	$ (0.15)	$ 0.24	$ 0.34	$ 0.31	$ 0.54	$ 0.26	$ 1.43	$ 1.46
Weighted Average Limited Partnership Units Outstanding, Basic										765,046	464,286	349,902
Partnership Interest [Member]
Earnings Per Share Basic [Line Items]
Weighted average common shares/units outstanding for basic EPS/EPU										169,997,000	167,990,000	170,074,000
Weighted average common shares/units outstanding for diluted EPS/EPU										170,225,000	168,235,000	170,450,000
Income per common share - basic										$ 0.27	$ 1.43	$ 1.47
Income per common share - diluted										$ 0.26	$ 1.43	$ 1.46
Continuing Operations [Member]
Earnings Per Share Basic [Line Items]
Income attributable to common stockholders/unit holders - basic										$ 44,889	$ 239,430	$ 249,127
Income attributable to common stockholders/unit holders - diluted										44,889	239,430	249,127
Continuing Operations [Member] | Partnership Interest [Member]
Earnings Per Share Basic [Line Items]
Income attributable to common stockholders/unit holders - basic										45,092	240,064	249,652
Income attributable to common stockholders/unit holders - diluted										$ 45,092	$ 240,064	$ 249,652

[1]   ⁽¹⁾ Includes the dilutive impact of unvested restricted stock.     ⁽²⁾ Using the treasury stock method, 2019 weighted average common shares outstanding for basic and diluted earnings per share exclude 1.9 million shares issuable under the forward ATM equity offering as they would be anti-dilutive.  These shares are included in 2020 weighted average common shares outstanding as they were settled in March 2020.