| Company | Ranking | Outlook | Date |
|---|---|---|---|
| S&P | AA | Steady | Apr 21 2023 |
| DBRS | AA | Steady | Jan 13 2023 |
| Moody’s | Aa3 | Damaging | Oct 21 2022 |
| DBRS | AA (excessive) | Below Assessment | Oct 19 2022 |
| Fitch | AA- | Damaging | Oct 05 2022 |
| S&P | AA | Damaging | Sep 30 2022 |
| Fitch | AA- | Steady | Jun 18 2021 |
| DBRS | AA (excessive) | Steady | Nov 13 2020 |
| Moody’s | Aa3 | Steady | Oct 16 2020 |
| DBRS | AAA | Damaging | Might 15 2020 |
| Fitch | AA- | Damaging | Mar 27 2020 |
| Fitch | AA | Damaging | Dec 17 2019 |
| S&P | AA | Steady | Dec 17 2019 |
| Moody’s | Aa2 | Damaging | Nov 08 2019 |
| Fitch | AA | Damaging Watch | Feb 20 2019 |
| Moody’s | Aa2 | Steady | Sep 22 2017 |
| Fitch | AA | Damaging | Jun 28 2016 |
| S&P | AA | Damaging | Jun 27 2016 |
| Moody’s | Aa1 | Damaging | Jun 24 2016 |
| S&P | AAA | Damaging | Jun 12 2015 |
| S&P | AAA | Steady | Jun 13 2014 |
| Fitch | AA+ | Steady | Apr 19 2013 |
| Moody’s | Aa1 | Steady | Feb 22 2013 |
| S&P | AAA | Damaging | Dec 13 2012 |
| Fitch | AAA | Damaging | Mar 14 2012 |
| Moody’s | Aaa | Damaging | Feb 13 2012 |
| S&P | AAA | Steady | Oct 26 2010 |
| DBRS | AAA | Steady | Jul 19 2010 |
| S&P | AAA | Damaging | Might 21 2009 |
| Fitch | AAA | Steady | Sep 21 2000 |
| Fitch | AAA | Steady | Sep 21 2000 |
| Fitch | AAA | N/A | Aug 10 1994 |
| S&P | AAA | Steady | Jun 26 1989 |
| S&P | AAA | N/A | Apr 28 1978 |
| Moody’s | Aaa | Steady | Mar 31 1978 |
