| Date | Acquired | Amount |
|---|---|---|
| Jan 09, 2017 | Undisclosed amount | |
| Sep 08, 2016 | Undisclosed amount | |
| Jul 26, 2016 | Undisclosed amount | |
| Apr 08, 2015 | $ 161,500,000 | |
| Jan 12, 2015 | $ 89,400,000 | |
| Dec 01, 2014 | Undisclosed amount | |
| Nov 10, 2014 | Undisclosed amount | |
| Oct 20, 2014 | Undisclosed amount | |
| Sep 16, 2014 | Undisclosed amount | |
| Aug 31, 2014 | Undisclosed amount | |
| Jan 08, 2014 | $ 24,200,000 | |
| Dec 11, 2013 | Undisclosed amount | |
| Sep 03, 2013 | Undisclosed amount | |
| Dec 06, 2012 | $ 355,000,000 | |
| Sep 10, 2012 | Undisclosed amount | |
| Jun 13, 2012 | $ 399,500,000 | |
| May 09, 2012 | Undisclosed amount | |
| Apr 20, 2012 | $ 53,000,000 | |
| Oct 26, 2011 | $ 91,300,000 | |
| Oct 13, 2011 | $ 54,500,000 | |
| Aug 10, 2011 | $ 32,200,000 | |
| Jul 12, 2011 | $ 158,800,000 | |
| May 23, 2011 | Undisclosed amount | |
| Feb 22, 2011 | Undisclosed amount | |
| Dec 17, 2010 | $ 107,500,000 | |
| Aug 31, 2010 | $ 13,200,000 | |
| Feb 23, 2010 | Undisclosed amount | |
| Nov 18, 2008 | $ 26,600,000 | |
| May 20, 2008 | Undisclosed amount | |
| Aug 15, 2007 | $ 500,000,000 | |
| Jun 11, 2007 | Undisclosed amount | |
| Mar 14, 2007 | Undisclosed amount | |
| Jan 08, 2007 | $ 51,700,000 | |
| Aug 21, 2006 | $ 50,000,000 | |
| May 08, 2006 | $ 68,000,000 | |
| Nov 15, 2005 | Undisclosed amount | |
| Aug 16, 2005 | Undisclosed amount | |
| Nov 23, 2004 | $ 50,000,000 | |
| Dec 18, 2003 | $ 225,000,000 | |
| Jan 02, 2002 | $ 32,000,000 | |
| Mar 21, 2001 | $ 184,600,000 | |
| Feb 17, 2000 | $ 47,800,000 | |
| Jul 01, 1998 | $ 8,000,000 | |
| Feb 06, 1998 | $ 17,500,000 | |
| Sep 09, 1997 | $ 5,000,000 |