| Current (1) |
| Chairman | 2010 |
| Former (19) |
| Board of Directors | 2014 – 2016 |
| Board of Directors | 1999 – 2002 |
| Board of Directors | 2000 – 2003 |
| Chairman | 2007 – 2009 |
| Board of Directors | 1975 – 1998 |
| Board of Directors | 2018 – 2019 |
| Chairman | 1995 – 2000 |
| Chairman | 1975 – 1991 |
| Board of Directors | 2016 – 2017 |
| Chairman | 2009 – 2010 |
| Board of Directors | 2002 – 2007 |
| Board of Directors | 1975 – 1991 |
| Board of Directors | 2010 – 2012 |
| Board of Directors | 2003 – 2008 |
| Board of Directors | 1975 – 2003 |
| Board of Directors | 2007 – 2010 |
| Board of Directors | 2013 – 2014 |
| Board of Directors | 2012 – 2013 |
| Board of Directors | 2010 – 2013 |