Credit Risk and Fair Value of Financial Instruments (Details) - USD ($)
$ in Thousands |
Sep. 30, 2016 |
Dec. 31, 2015 |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Bank Credit Facility |
$ 0
|
$ 270,000
|
| Total fair value of debt instruments |
3,263,095
|
3,101,760
|
| June 2017 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Senior Notes |
0
|
314,618
|
| October 2018 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Senior Notes |
279,375
|
279,375
|
| November 2020 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Senior Notes |
205,100
|
201,500
|
| November 2021 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Senior Notes |
179,343
|
176,438
|
| January 2022 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Senior Notes |
442,616
|
445,188
|
| May 2024 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Senior Notes |
907,375
|
884,094
|
| April 2027 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Senior Notes |
238,000
|
216,500
|
| July 2018 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Notes Payable, Fair Value Disclosure |
0
|
310,000
|
| March 2021 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Bank Credit Facility |
325,000
|
0
|
| Notes Payable, Fair Value Disclosure |
682,500
|
0
|
| Mortgages [Member] |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Notes Payable, Fair Value Disclosure |
$ 3,786
|
$ 4,047
|