Senior Unsecured Notes (Summary Of Senior Unsecured Notes) (Details) - USD ($)
|
12 Months Ended |
|
Dec. 31, 2018 |
Dec. 31, 2017 |
| Debt Instrument [Line Items] |
|
|
| Principal balance outstanding |
$ 2,792,651,000
|
$ 2,809,568,000
|
| Adjustment for unamortized debt discount |
(2,838,000)
|
|
| Total senior unsecured notes, net |
$ 2,792,651,000
|
|
| 4.500% Senior Unsecured Notes Due April 18, 2022 [Member] |
|
|
| Debt Instrument [Line Items] |
|
|
| Interest rate of senior unsecured notes |
4.50%
|
|
| Maturity date of the senior unsecured notes |
Apr. 18, 2022
|
|
| 3.150% Senior Unsecured Notes, Due May 15, 2023 [Member] |
|
|
| Debt Instrument [Line Items] |
|
|
| Interest rate of senior unsecured notes |
3.15%
|
|
| Maturity date of the senior unsecured notes |
May 15, 2023
|
|
| Unsecured Note [Member] |
|
|
| Debt Instrument [Line Items] |
|
|
| Principal balance outstanding |
$ 575,000,000
|
575,000,000
|
| Adjustment for unamortized debt discount |
(2,838,000)
|
(3,505,000)
|
| Unamortized deferred financing costs |
(1,848,000)
|
(2,350,000)
|
| Total senior unsecured notes, net |
570,314,000
|
569,145,000
|
| Unsecured Note [Member] | 4.500% Senior Unsecured Notes Due April 18, 2022 [Member] |
|
|
| Debt Instrument [Line Items] |
|
|
| Principal balance outstanding |
$ 300,000,000
|
300,000,000
|
| Effective rate |
4.612%
|
|
| Unsecured Note [Member] | 3.150% Senior Unsecured Notes, Due May 15, 2023 [Member] |
|
|
| Debt Instrument [Line Items] |
|
|
| Principal balance outstanding |
$ 275,000,000
|
$ 275,000,000
|
| Effective rate |
3.517%
|
|