Investments in Real Estate (Details) (USD $)	9 Months Ended			12 Months Ended	9 Months Ended
	Sep. 30, 2012 sqft	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2011 Maximum	Sep. 30, 2012 New properties and properties under development item sqft	Sep. 30, 2011 New properties and properties under development item sqft	Sep. 30, 2012 Aggregate acquisitions item	Sep. 30, 2011 Aggregate acquisitions item	Sep. 30, 2012 American Realty Capital Trust, Inc. item	Sep. 30, 2012 Real estate investments with existing leases item	Sep. 30, 2011 Real estate investments with existing leases item
Investments in real estate properties
Investments in properties					$ 717,600,000	$ 826,400,000				$ 351,700,000	$ 573,100,000
Investment in entity									2,950,000,000
Number of properties acquired					234	125			500	78	93
Initial weighted average contractual lease rate of properties acquired (as a percent)					7.10%	7.90%
Number of states in which properties are located					33	25
Leasable square feet	34,300,000				7,000,000	5,500,000
Leased area (as a percent)					100.00%	100.00%
Average lease term					14 years 3 months 18 days	11 years 3 months 18 days
Number of industries in which tenants operate					19	15
Investments to any one tenant as a percentage of total assets				10.00%
Acquisition transaction costs					1,400,000	1,100,000
Land recorded related to acquisition							179,800,000	173,400,000
Buildings and improvements recorded							516,200,000	528,300,000
Intangible assets recorded							49,600,000	129,900,000
Intangible assets and assumed liabilities recorded							28,000,000	5,200,000
Premiums recorded upon assumption of mortgages							7,100,000	820,000
Number of properties acquired with assumed mortgages payable							5	4
Amount of investment allocated by estimate					98,300,000
Number of properties acquired with notes receivable								1
Assumed mortgages payable	133,394,000		67,781,000				70,000,000	67,400,000
Assumed note receivable	8,780,000		8,780,000					8,800,000
Total capitalized costs on existing properties	4,500,000	3,000,000
Re-leasing costs included in capitalized costs on existing properties	1,200,000	1,300,000
Building and tenant improvements included in capitalized costs on existing properties	3,300,000	1,700,000
Intangible value of the in-place leases acquired										47,100,000	107,600,000
Intangible value of above-market leases acquired										2,500,000	22,300,000
Intangible value of below-market leases acquired										19,500,000	3,500,000
Intangible value of above and below-market leases amortized as net decrease to rental income	1,400,000	669,000
Intangible value of in-place leases amortized to expense	10,300,000	5,000,000
Exchange ratio for each share of ARCT									0.2874
Merger related costs									$ 5,500,000