The following is a summary of investment securities as of December 31:
| 2013 | 2012 | |||||||||||||||||||||||
| Gross | Gross | Estimated | Gross | Gross | Estimated | |||||||||||||||||||
| Unrealized | Unrealized | Fair | Unrealized | Unrealized | Fair | |||||||||||||||||||
| Description of Securities (Millions) | Cost | Gains | Losses | Value | Cost | Gains | Losses | Value | ||||||||||||||||
| State and municipal obligations | $ | 4,060 | $ | 54 | $ | (79) | $ | 4,035 | $ | 4,280 | $ | 199 | $ | (5) | $ | 4,474 | ||||||||
| U.S. Government agency obligations | 3 | ― | ― | 3 | 3 | ― | ― | 3 | ||||||||||||||||
| U.S. Government treasury obligations | 318 | 3 | (1) | 320 | 330 | 8 | ― | 338 | ||||||||||||||||
| Corporate debt securities | 43 | 3 | ― | 46 | 73 | 6 | ― | 79 | ||||||||||||||||
| Mortgage-backed securities (a) | 160 | 5 | (1) | 164 | 210 | 14 | ― | 224 | ||||||||||||||||
| Equity securities (b) | 29 | 95 | ― | 124 | 64 | 232 | ― | 296 | ||||||||||||||||
| Foreign government bonds and obligations | 272 | 5 | (1) | 276 | 134 | 15 | ― | 149 | ||||||||||||||||
| Other (c) | 50 | ― | (2) | 48 | 51 | ― | ― | 51 | ||||||||||||||||
| Total | $ | 4,935 | $ | 165 | $ | (84) | $ | 5,016 | $ | 5,145 | $ | 474 | $ | (5) | $ | 5,614 | ||||||||