Year Ended December 31, | |||||||||||
2013 | 2012 | 2011 | |||||||||
Balance as of beginning of year | $ | 108 | $ | 87 | $ | 101 | |||||
Additions to accrual | 2 | 14 | 3 | ||||||||
Revisions in estimated cash flows | — | 13 | 1 | ||||||||
Accretion expense | 2 | 5 | 4 | ||||||||
Settlements | (1 | ) | (11 | ) | (22 | ) | |||||
Separation of retail business | (80 | ) | — | — | |||||||
Balance as of end of year | $ | 31 | $ | 108 | $ | 87 | |||||