| Date | Acquired | Amount |
|---|---|---|
| Feb 23, 2017 |
|
$ 800,000,000 |
| Apr 22, 2015 |
|
$ 2,100,000,000 |
| Apr 20, 2014 |
|
Undisclosed amount |
| Oct 11, 2011 |
|
$ 172,000,000 |
| Sep 22, 2009 |
|
$ 20,000,000 |
| Sep 01, 2009 |
|
Undisclosed amount |
| Dec 14, 2007 |
|
$ 730,000,000 |
| Mar 03, 2003 |
|
Undisclosed amount |
