Debt - Summary of the Components of Interest Expense Related to the Company's Borrowings (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Schedule Of Interest Expenses [Line Items]                      
Amortization of deferred financing costs                 $ 5,899 $ 13,188 $ 2,819
Amortization of net losses related to interest rate swaps                 125 11 3,415
Amortization of debt (premium)/discount                 (849) 4,653 10,900
Total interest expense 56,144 53,535 55,992 54,399 52,890 50,386 39,552 36,439 220,070 179,267 156,220
Revolving Credit Facilities [Member]                      
Schedule Of Interest Expenses [Line Items]                      
Interest expense                 3,597 3,037 108
Mortgages and Notes Payable [Member]                      
Schedule Of Interest Expenses [Line Items]                      
Interest expense                 196,246 157,903 119,196
Convertible Notes [Member]                      
Schedule Of Interest Expenses [Line Items]                      
Interest expense                 15,046 0 0
Other Interest Expense [Member]                      
Schedule Of Interest Expenses [Line Items]                      
Interest expense                 6 475 10
Term Note Payable [Member]                      
Schedule Of Interest Expenses [Line Items]                      
Interest expense                 0 0 19,925
Interest Expense [Member]                      
Schedule Of Interest Expenses [Line Items]                      
Amortization of debt (premium)/discount                 $ (849) $ 4,653 $ 10,747