Investments - Summary of Gross Real Estate and Loan Activity (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Property
Dec. 31, 2013
Property
Number of Properties Owned or Financed    
Beginning balance 2,186 1,207
Acquisitions/improvements 361 194
Acquisitions/improvements and loan originations - Cole/Merger   816
Dispositions of real estate (38) (22)
Principal payments and payoffs 0 (9)
Impairments 0 0
Write off of gross lease intangibles 0  
Loan premium amortization and other 0 0
Ending balance 2,509 2,186
Dollar Amount of Investments    
Beginning balance $ 7,235,732 $ 3,654,925
Acquisitions/improvements 973,653 422,458
Acquisitions/improvements and loan originations - Cole/Merger   3,580,108
Dispositions of real estate (117,755) (396,717)
Principal payments and payoffs (5,771) (15,254)
Impairments (35,908) (7,233)
Write off of gross lease intangibles (2,748)  
Loan premium amortization and other (2,840) (2,555)
Ending balance $ 8,044,363 $ 7,235,732