We are party to derivative contracts through certain of our subsidiaries. Currently, the most significant derivative contracts consist of equity index put option contracts. The liabilities and related notional values of these contracts follows (in millions).

Liabilities

Notional

Value

December 31, 2019

968

14,385

December 31, 2018

2,452

26,759

Notional value represents the aggregate undiscounted amounts payable assuming that the value of each index is zero at each contract’s expiration date. Certain of these contracts are denominated in foreign currencies. Notional amounts are based on the foreign currency exchange rates as of each balance sheet date.

We recorded derivative contract gains of $1,484 million in 2019, losses of $300 million in 2018 and gains of $718 million in 2017, with respect to our equity index put option contracts. The gains in 2019 were primarily due to increases in equity index values.

The equity index put option contracts are European style options written prior to March 2008 on four major equity indexes. During 2019, contracts with notional values of approximately $12.3 billion expired and substantially all of the remaining contracts will expire by February 2023. At December 31, 2019, the remaining weighted average life of all contracts was approximately 1.8 years. We received aggregate premiums of $2.5 billion on the remaining contracts at the contract inception dates and we have no counterparty credit risk. Future payments, if any, under any given contract will be required if the prevailing index value is below the contract strike price at the expiration date. The aggregate intrinsic value (the undiscounted liability assuming the contracts are settled based on the index values and foreign currency exchange rates as of the balance sheet date) was $397 million at December 31, 2019 and $1,653 million at December 31, 2018. These contracts may not be unilaterally terminated or fully settled before the expiration dates and the ultimate amount of cash basis gains or losses on these contracts will not be determined until the contract expiration dates.

Our regulated utility subsidiaries may use forward purchases and sales, futures, swaps and options to manage a portion of their commodity price risks. Most of these net derivative contract assets or liabilities of our regulated utilities are probable of recovery through rates and are offset by regulatory liabilities or assets. Derivative contract assets were $145 million and $172 million at December 31, 2019 and 2018, respectively. Derivative contract liabilities were $76 million and $111 million at December 31, 2019 and 2018, respectively.