The following table summarizes the costs incurred on our collaborative research and development agreements and revenue contracts (in thousands):
| December 31, | |||||||||
| 2013 | 2012 | ||||||||
| Costs and estimated earnings incurred on uncompleted contracts | $ | 2,909 | $ | 1,977 | |||||
| Billings on uncompleted contracts | (3,589) | (2,063) | |||||||
| $ | (680) | $ | (86) | ||||||
| Included in accompanying consolidated balance sheets under the following captions: | |||||||||
| Costs and estimated earnings in excess of billings on uncompleted contracts | $ | - | $ | 12 | |||||
| Billings in excess of costs and estimated earnings on uncompleted | |||||||||
| contracts | (680) | (98) | |||||||
| $ | (680) | $ | (86) | ||||||