(dollars in millions) | 2013 | 2012 | 2011 | ||||||||
Balance at January 1 | $ | 1,073 | $ | 946 | $ | 891 | |||||
Additions for tax positions related to the current year | 113 | 232 | 71 | ||||||||
Additions for tax positions of prior years | 211 | 221 | 71 | ||||||||
Reductions for tax positions of prior years | (41 | ) | (21 | ) | (24 | ) | |||||
Settlements | (133 | ) | (305 | ) | (63 | ) | |||||
Balance at December 31 | $ | 1,223 | $ | 1,073 | $ | 946 | |||||
Gross interest expense related to unrecognized tax benefits | $ | 51 | $ | 40 | $ | 23 | |||||
Total accrued interest balance at December 31 | $ | 262 | $ | 270 | $ | 165 | |||||