Investments in Real Estate (Details) (USD $)	12 Months Ended																					1 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended
	Dec. 31, 2013 item sqft	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Pro Forma	Dec. 31, 2012 Pro Forma	Dec. 31, 2013 ARCT item sqft	Dec. 31, 2012 ARCT	Dec. 31, 2013 ARCT Retail properties	Dec. 31, 2013 ARCT Office properties	Dec. 31, 2013 ARCT Industrial and distribution properties	Dec. 31, 2013 Maximum	Dec. 31, 2013 New properties and properties under development or expansion item sqft	Dec. 31, 2012 New properties and properties under development or expansion item sqft	Dec. 31, 2013 New properties and properties under development or expansion Retail properties	Dec. 31, 2012 New properties and properties under development or expansion Retail properties	Dec. 31, 2013 New properties and properties under development or expansion Office properties	Dec. 31, 2012 New properties and properties under development or expansion Office properties	Dec. 31, 2013 New properties and properties under development or expansion Industrial and distribution properties	Dec. 31, 2012 New properties and properties under development or expansion Industrial and distribution properties	Dec. 31, 2013 New properties and properties under development or expansion Manufacturing properties	Dec. 31, 2012 New properties and properties under development or expansion Manufacturing properties	Sep. 30, 2013 New properties San Diego, CA	Dec. 31, 2013 Properties under development or expansion item	Dec. 31, 2012 Aggregate acquisitions	Dec. 31, 2013 Aggregate acquisitions item	Dec. 31, 2012 Aggregate acquisitions item	Dec. 31, 2013 Investments in Existing Properties item	Dec. 31, 2012 Investments in Existing Properties
Investments in real estate properties
Investments in properties																						$ 45,400,000	$ 39,600,000
Real estate acquired						3,200,000,000						1,510,000,000	1,160,000,000												4,670,000,000		4,320,000,000
Number of properties						515						459	439										21		974		799
Initial weighted average contractual lease rate of properties acquired (as a percent)												7.10%	7.20%										8.50%
Number of states in which properties are located						44						40	38
Leasable square feet	62,600,000					16,000,000						9,000,000	10,500,000
Leased area (as a percent)						100.00%						100.00%	100.00%
Weighted average lease term						12 years 2 months 12 days						14 years	13 years 9 months 18 days
Number of tenants						69
Number of industries in which tenants operate						28						23	23
Property type- percentage of properties acquired								54.00%	13.40%	32.60%				83.80%	79.60%	9.20%	0.80%	4.90%	11.30%	2.10%	8.30%
Acquisition transaction costs						13,000,000	7,900,000					2,100,000	2,400,000
Number of investments in properties that caused any tenant to be 10% of more of total assets	0
Investments to any one tenant as a percentage of total assets											10.00%
Land recorded related to acquisition																								289,200,000	805,500,000	289,200,000
Buildings and improvements recorded																								768,400,000	3,210,000,000	768,400,000
Intangible assets related to leases recorded																								104,800,000	772,700,000	104,800,000
Other assets recorded																								34,900,000	13,600,000	34,900,000
Intangible liabilities related to leases and other assumed liabilities recorded																								33,200,000	128,600,000	33,200,000
Premiums recorded upon assumption of mortgages																								10,000,000	28,400,000	10,000,000
Number of properties acquired with assumed mortgages payable																										8
Assumed mortgages payable	783,360,000	175,868,000																						110,500,000		110,500,000
Contingent consideration associated with acquisition	0	0
Total revenue	778,375,000	482,847,000	412,360,000																						225,300,000	23,900,000
Income from continuing operations	179,180,000	140,719,000	139,622,000																						44,000,000	9,800,000
Amount of investment allocated by estimate																									120,800,000
Amount of investment previously allocated by estimate finalized during the period																								106,400,000
Total capitalized costs on existing properties	10,211,675																										8,500,000	6,600,000
Re-leasing costs included in capitalized costs on existing properties																											1,300,000	1,620,000
Building and tenant improvements included in capitalized costs on existing properties																											7,200,000	4,930,000
Intangible value of the in-place leases acquired	843,616,000	235,914,000																									602,800,000
Intangible value of above-market leases acquired	207,641,000	40,389,000																									169,900,000
Intangible value of below-market leases acquired																											128,600,000
In-place lease, depreciation and amortization to expense	65,500,000	15,600,000	8,300,000
Net (increase) decrease to rental income for capitalized above market and below market leases	8,200,000	1,800,000	1,100,000
Net decrease to rental revenue
2014	(7,708,000)
2015	(7,785,000)
2016	(7,797,000)
2017	(7,794,000)
2018	(7,535,000)
Thereafter	(58,000)
Totals	(38,677,000)
Increase to amortization expense
2014	75,164,000
2015	72,616,000
2016	72,210,000
2017	70,986,000
2018	68,649,000
Thereafter	388,907,000
Totals	748,532,000
Merger-related costs					12,500,000
Pro Forma Information
Total revenue				848,600,000	772,600,000
Income from continuing operations				$ 223,300,000	$ 212,800,000