| Date | Acquired | Amount |
|---|---|---|
| Nov 16, 2011 | Undisclosed amount | |
| Oct 24, 2011 | Undisclosed amount | |
| Jun 06, 2011 | Undisclosed amount | |
| May 05, 2011 | Undisclosed amount | |
| Feb 14, 2011 | Undisclosed amount | |
| Nov 09, 2010 | $ 55,000,000 | |
| Oct 02, 2010 | $ 35,000,000 | |
| Jul 12, 2010 | Undisclosed amount | |
| Dec 03, 2009 | Undisclosed amount | |
| Jan 13, 2009 | Undisclosed amount | |
| Sep 12, 2008 | Undisclosed amount | |
| Sep 11, 2008 | Undisclosed amount | |
| Aug 15, 2008 | Undisclosed amount | |
| Jan 21, 2008 | Undisclosed amount | |
| Dec 10, 2007 | Undisclosed amount | |
| Nov 01, 2007 | Undisclosed amount | |
| Oct 18, 2007 | Undisclosed amount | |
| Jun 22, 2007 | $ 90,000,000 | |
| May 21, 2007 | Undisclosed amount | |
| Jan 09, 2006 | $ 45,000,000 | |
| Jul 12, 2005 | $ 56,500,000 | |
| Apr 26, 2005 | $ 61,000,000 | |
| Mar 18, 2004 | $ 115,000,000 | |
| Oct 23, 2002 | $ 51,700,000 | |
| Mar 14, 2002 | Undisclosed amount | |
| Jun 29, 2000 | Undisclosed amount | |
| Apr 19, 2000 | Undisclosed amount | |
| Nov 12, 1999 | $ 83,400,000 |