| | | 2013 | | 2012 | | 2011 |
| | | | (in millions) |
Fixed maturities, available-for-sale | | $ | 10,541 | | $ | 9,800 | | $ | 9,374 |
Fixed maturities, held-to-maturity | | | 125 | | | 135 | | | 140 |
Equity securities, available-for-sale | | | 337 | | | 332 | | | 315 |
Trading account assets | | | 963 | | | 890 | | | 889 |
Commercial mortgage and other loans | | | 1,985 | | | 2,014 | | | 1,926 |
Policy loans | | | 611 | | | 597 | | | 598 |
Short-term investments and cash equivalents | | | 40 | | | 46 | | | 58 |
Other long-term investments | | | 710 | | | 320 | | | 231 |
| Gross investment income | | | 15,312 | | | 14,134 | | | 13,531 |
Less: investment expenses | | | (583) | | | (473) | | | (407) |
| Net investment income | | $ | 14,729 | | $ | 13,661 | | $ | 13,124 |