2013 | 2012 (1) | ||||||
Beginning balance as of January 1, | $ | 435,624 | $ | 344,180 | |||
Additions | 94,651 | 59,747 | |||||
Accretion expense | 34,045 | 25,056 | |||||
Revisions in estimates (2) | (36,492 | ) | 6,641 | ||||
Settlements | (959 | ) | — | ||||
Balance as of December 31, | $ | 526,869 | $ | 435,624 | |||
(1) | December 31, 2012 balances have been revised to reflect purchase accounting measurement period adjustments. |
(2) | For the year ended December 31, 2013, revisions in estimates include the impact of approximately $19.8 million of foreign currency translation. |