Organization - Narrative (Details) (USD $)
 9 Months Ended 9 Months Ended 0 Months Ended 0 Months Ended 0 Months Ended 0 Months Ended 0 Months Ended 3 Months Ended 9 Months Ended
Sep. 30, 2014
Property
Dec. 31, 2013
Property
Sep. 30, 2014
Current Year Acquisitions
Property
May 20, 2014
Convertible Senior Notes
May 20, 2014
2.875% Convertible Senior Notes due 2019
Convertible Senior Notes
May 20, 2014
3.75% Convertible Senior Notes due 2021
Convertible Senior Notes
May 20, 2014
Old Notes
Mortgages
May 20, 2014
New Notes
Mortgages
May 20, 2014
Master trust notes
Senior Mortgage Notes Payable
May 20, 2014
Master trust notes
Net-lease Mortgage Notes
May 20, 2014
Master trust notes
Old Notes
Jun. 05, 2014
Subsidiaries
Subsidiary
Sep. 30, 2014
Subsidiaries
Mortgages
Jun. 04, 2014
Subsidiaries
Mortgages
Property
Jun. 05, 2014
Subsidiaries
Master trust notes
May 20, 2014
Underwriters
2.875% Convertible Senior Notes due 2019
Convertible Senior Notes
May 20, 2014
Underwriters
3.75% Convertible Senior Notes due 2021
Convertible Senior Notes
May 20, 2014
Secondary Offering
May 20, 2014
Secondary Offering
May 20, 2014
Over-Allotment Option
May 16, 2014
Over-Allotment Option
Sep. 30, 2014
At the Market
Jun. 30, 2014
At the Market
Apr. 15, 2014
At the Market
Sep. 30, 2014
General Partner
Sep. 30, 2014
Limited Partner
Summary Of Business And Significant Accounting Policies [Line Items]                                                    
Percentage ownership of operating partnership                                                 1.00% 99.00%
Real estate properties and loans, gross $ 7,705,490,000 [1] $ 7,235,732,000 [1]                                                
Real estate assets held for sale 2,408 2,186                                                
Gross investment in real estate, percentage 98.60%                                                  
Number of owned real estate properties 2,263 2,041                                                
Securing mortgage properties, percentage 1.40%                                                  
Securing mortgage properties 145 145                                                
Issuance of common shares (in shares)                                   26,450,000   3,450,000   0 1,574,320      
Common stock, par value per share (in USD per share) $ 0.01 $ 0.01                                 $ 0.01              
Common stock option to purchase additional shares to cover over-allotments term                                         30 days          
Aggregate principal amount of debt         402,500,000.0 345,000,000.0               545,700,000.0   52,500,000.0 45,000,000.0                  
Stated Rate         2.875% 3.75%               6.59%                        
Proceeds from issuance of common stock                                   271,200,000         16,300,000      
Proceeds from convertible debt       726,200,000                                            
Amount of debt defeasance                 509,800,000 18,000,000         488,700,000                      
Minimum percent to exchange notes                     98.00%                              
Total debt, net 4,007,828,000 3,778,218,000         912,400,000                                      
Amount of old debt notes exchanged                     894,400,000                              
Percentage elected to exchange notes                     98.00%                              
Extended term of debt               17 years                                    
Number of indirectly owned subsidiaries that defeased loans outstanding under master loan agreement                       2                            
Number of properties securing borrowings                           112                        
Gross book value of rental properties and rent                         917,700,000                          
Maximum authorized proceeds from issuance of common stock                                               350,000,000.0    
Number of properties acquired     241                                              
Payments to acquire real estate     572,200,000                                              
Revenues     2,400,000                                              
Number of properties disposed of, including continuing and discontinued operations 19                                                  
Proceeds from sale of real estate $ 44,900,000                                                  
[1] The dollar amount of investments includes the gross investment in land, buildings and lease intangibles, as adjusted for any impairment, related to properties owned and the carrying amount of loans receivable and real estate assets held under direct financing leases.