| Current (2) |
| Board of Directors | 2019 |
| Chairman | 2019 |
| Former (14) |
| Chairman | 2013 – 2017 |
| Board of Directors | 1974 – 1991 |
| Board of Directors | 1974 – 2003 |
| Board of Directors | 2007 – 2013 |
| Chairman | 2004 – 2007 |
| Board of Directors | 2013 – 2016 |
| Board of Directors | 1974 – 1988 |
| Board of Directors | 2004 – 2007 |
| Chairman | 2019 – 2019 |
| Board of Directors | 1974 – 1995 |
| Board of Directors | 2003 – 2009 |
| Chairman | 1974 – 2004 |
| Chairman | 2007 – 2011 |
| Board of Directors | 1974 – 2003 |