| Gross unrecognized tax benefits | 2013 | 2012 | 2011 | |||
| (millions of dollars) | ||||||
| Balance at January 1 | 7,663 | 4,922 | 4,148 | |||
| Additions based on current year's tax positions | 1,460 | 1,662 | 822 | |||
| Additions for prior years' tax positions | 464 | 2,559 | 451 | |||
| Reductions for prior years' tax positions | (249) | (535) | (329) | |||
| Reductions due to lapse of the statute of limitations | (588) | (79) | - | |||
| Settlements with tax authorities | (849) | (855) | (145) | |||
| Foreign exchange effects/other | (63) | (11) | (25) | |||
| Balance at December 31 | 7,838 | 7,663 | 4,922 | |||