17)

OTHER CURRENT AND NON-CURRENT LIABILITIES

As of December 31, 2018 and 2017, consolidated other current liabilities were as follows:


		2018		2017
Provisions¹	Ps		10,509		12,121
Interest payable			1,856		2,496
Advances from customers			3,838		3,886
Other accounts payable and accrued expenses²			5,222		5,123
Contract liabilities with customers (note 3)			775		770

	Ps		22,200		24,396

1	Current provisions primarily consist of accrued employee benefits, insurance payments, accruals for legal assessments and others. These amounts are revolving in nature and are expected to be settled and replaced by similar amounts within the next 12 months.

2	In 2017, includes an account payable in Colombian pesos equivalent to Ps491 (US$25) settled on January 5, 2018 related to a penalty imposed by the Commerce and Industry Superintendence in Colombia in connection with a market investigation (note 24.2).

As of December 31, 2018 and 2017, consolidated other non-current liabilities were as follows:


		2018		2017
Asset retirement obligations¹	Ps		8,013		7,906
Accruals for legal assessments and other responsibilities²			879		1,599
Non-current liabilities for valuation of derivative instruments			406		402
Environmental liabilities³			573		991
Other non-current liabilities and provisions⁴			5,134		4,751

	Ps		15,005		15,649

1	Provisions for asset retirement include future estimated costs for demolition, cleaning and reforestation of production sites at the end of their operation, which are initially recognized against the related assets and are depreciated over their estimated useful life.

2	Provisions for legal claims and other responsibilities include items related to tax contingencies.

3	Environmental liabilities include future estimated costs arising from legal or constructive obligations, related to cleaning, reforestation and other remedial actions to remediate damage caused to the environment. The expected average period to settle these obligations is greater than 15 years.

As of December 31, 2018 and 2017, includes Ps981 and Ps1,498, respectively, of the non-current portion of taxes payable in Mexico recognized in connection with the termination of the tax consolidation regime in 2014. As of December 31, 2018 and 2017, Ps590 and Ps958, respectively, were included within current taxes payable.

Changes in consolidated other current and non-current liabilities for the years ended December 31, 2018 and 2017, were as follows:


		2018
		Asset retirement obligations			Environmental liabilities			Accruals for legal proceedings			Valuation of derivative instruments			Other liabilities and provisions			Total			2017
Balance at beginning of period	Ps		7,906			991			1,599			421			17,623			28,540			28,937
Business combinations			—			—			—			—			—			—			345
Additions or increase in estimates			1,355			11			136			275			25,379			27,156			41,137
Releases or decrease in estimates			(916	)		(4	)		(807	)		—			(26,841	)		(28,568	)		(41,700	)
Reclassifications			(22	)		(384	)		—			(96	)		124			(378	)		(1,148	)
Accretion expense			(186	)		—			—			—			(902	)		(1,088	)		(1,021	)
Foreign currency translation			(124	)		(41	)		(49	)		78			763			627			1,990

Balance at end of period	Ps		8,013			573			879			678			16,146			26,289			28,540

Out of which:
Current provisions	Ps		297			—			—			272			10,715			11,284			12,891