Retirement tax questions

I'm uncertain what a cost basis is. On our 1099-R, we have a figure for Employee Contributions (about $200K). Each year, we get to take about $5K off of the annual distributions to reduce our taxable income. Besides these numbers, the 1099-R only ever lists Federal and state taxes paid, and the amount paid for health insurance premiums. There are no figures on it for anything like a cost basis.