Investments - Market value of investments listed in regulated stock markets (Details) - EUR (€) € / shares in Units, € in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investments
Net carrying amount	€ 5,887	€ 6,749	€ 9,035
Joint ventures
Investments
Net carrying amount	€ 2,057	€ 2,832
Joint ventures \| Saipem SpA
Investments
Number of shares held	308,767,968
% of the investment	31.20%	31.08%
Share price	€ 1,845
Market value	€ 570
Net carrying amount	€ 137	€ 908

The amount of investments accounted for using the equity method. The equity method is a method of accounting whereby the investment is initially recognised at cost and adjusted thereafter for the post-acquisition change in the investor's share of net assets of the investee. The investor's profit or loss includes its share of the profit or loss of the investee. The investor's other comprehensive income includes its share of the other comprehensive income of the investee. [Refer: At cost [member]]

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