Other Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Income Tax Disclosure [Abstract]
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS	$ 12,384	[1]	$ 19,766	[2]	$ (24,205)	[3]	$ (999)	[4]	$ (6,391)	[5]	$ 5,814	[6]	$ 2,908	[7]	$ 3,134	[8]	$ 6,946		$ 5,465		$ (214)
Reconciling items to taxable income:
Depreciation and amortization																	26,240		28,526		21,479
Gain or loss on disposition of depreciable assets																	(3,656)		922		(85)
Impairments																	6,222		3,807		4,999
Straight-line rent																	(6,493)		(6,075)		(4,142)
Receivable allowances																	(716)		(74)		(299)
Stock-based compensation																	5,817		5,400		6,104
Other																	(1,866)		8,917		4,927
Reconciling items to taxable income, total																	25,548		41,423		32,983
Taxable income																	32,494	[9]	46,888	[9]	32,769	[9]
Dividends paid																	$ 111,571		$ 96,356		$ 89,270

[1] The increases in net income and amounts per share for the fourth quarter of 2013 are primarily attributable to gains on sales of real estate totaling $2.7 million.

[2] The increases in net income and amounts per share for the third quarter of 2013 are primarily attributable to gains on sales of real estate totaling $20.2 million, partially offset by impairment charges of $6.3 million.

[3] The decreases in net income and amounts per share for the second quarter of 2013 are primarily attributable to losses of extinguishment of debt of $29.9 million, of which $0.3 million is included in discontinued operations. This amount is partially offset by gains on sales of real estate totaling $1.8 million.

[4] The decreases in net income and amounts per share for the first quarter of 2013 are primarily attributable to impairment charges of $3.6 million.

[5] The decreases in net income and amounts per share for the fourth quarter of 2012 are primarily attributable to impairment charges of $7.7 million. This amount is partially offset by gains on sales of real estate totaling $1.2 million.

[6] The increases in net income and amounts per share for the third quarter of 2012 are primarily attributable to gains on sales of real estate totaling $6.3 million, partially offset by impairment charges of $2.9 million.

[7] The decreases in net income and amounts per share for the second quarter of 2012 are primarily attributable to impairment charges of $0.2 million.

[8] The increases in net income and amounts per share for the first quarter of 2012 are primarily attributable to gains on sales of real estate totaling $3.4 million and a lease termination fee totaling $1.5 million which is included in discontinued operations. This amount is partially offset by impairment charges of $4.2 million.

[9] Before REIT dividend paid deduction.