2013

2012

Asset retirement obligations, beginning of period

$

384,053

$

393,880

Liabilities settled

(81,543

) 

(112,827

) 

Accretion of discount

20,918

20,055

Disposition of properties

(19,564

) 

(3,993

) 

Liabilities assumed through acquisition

4,233

31,664

Liabilities incurred

1,745

1,815

Revisions of estimated liabilities due to Hurricane Ike

6,801

(20,616

) 

Revisions of estimated liabilities—all other

37,779

74,075

Asset retirement obligations, end of period

354,422

384,053

Less current portion

77,785

92,630

Long-term

$

276,637

$

291,423