| Date | Acquired | Amount |
|---|---|---|
| Feb 24, 2016 | Undisclosed amount | |
| Sep 04, 2015 | $ 425,000,000 | |
| Jul 22, 2015 | $ 250,000,000 | |
| Apr 21, 2015 | Undisclosed amount | |
| Sep 11, 2014 | Undisclosed amount | |
| Jul 29, 2014 | Undisclosed amount | |
| Mar 09, 2012 | Undisclosed amount | |
| Oct 07, 2011 | $ 100,000,000 | |
| Oct 01, 2011 | Undisclosed amount | |
| Jul 23, 2011 | Undisclosed amount | |
| Jun 07, 2011 | Undisclosed amount | |
| May 02, 2011 | Undisclosed amount | |
| Apr 27, 2011 | Undisclosed amount | |
| Mar 26, 2011 | Undisclosed amount | |
| Feb 14, 2011 | Undisclosed amount | |
| Dec 02, 2010 | Undisclosed amount | |
| Aug 24, 2010 | Undisclosed amount | |
| Jun 08, 2010 | Undisclosed amount | |
| Mar 26, 2010 | Undisclosed amount | |
| Aug 24, 2009 | Undisclosed amount | |
| Mar 24, 2009 | Undisclosed amount | |
| Feb 13, 2009 | Undisclosed amount | |
| Nov 15, 2007 | Undisclosed amount | |
| Nov 22, 2006 | Undisclosed amount | |
| Jul 15, 2006 | Undisclosed amount | |
| Mar 10, 2006 | Undisclosed amount | |
| Nov 16, 2001 | Undisclosed amount |