| Current (2) |
| Chairman | 2013 |
| Board of Directors | 2017 |
| Former (14) |
| Board of Directors | 1971 – 1993 |
| Board of Directors | 1971 – 1991 |
| Board of Directors | 1971 – 1995 |
| Board of Directors | 2013 – 2017 |
| Chairman | 1971 – 1989 |
| Board of Directors | 1971 – 2000 |
| Board of Directors | 1971 – 1991 |
| Board of Directors | 1971 – 1989 |
| Board of Directors | 2010 – 2015 |
| Chairman | 2000 – 2006 |
| Board of Directors | 2010 – 2017 |
| Board of Directors | 1971 – 1991 |
| Board of Directors | 2001 – 2003 |
| Board of Directors | 1971 – 1993 |