| Current (3) |
| Chairman | 2018 |
| Board of Directors | 2020 |
| Board of Directors | 2018 |
| Former (15) |
| Chairman | 2009 – 2011 |
| Chairman | 1973 – 1991 |
| Board of Directors | 1973 – 1993 |
| Chairman | 2011 – 2012 |
| Chairman | 2002 – 2006 |
| Chairman | 2006 – 2009 |
| Board of Directors | 2001 – 2009 |
| Chairman | 1996 – 2002 |
| Chairman | 2012 – 2018 |
| Board of Directors | 1998 – 2001 |
| Board of Directors | 1973 – 1998 |
| Board of Directors | 2002 – 2011 |
| Board of Directors | 1997 – 2002 |
| Chairman | 1973 – 1997 |
| Board of Directors | 2011 – 2013 |