| Cover | 12 Months Ended |
| Dec. 31, 2022 | |
| Document Information [Line Items] | |
| Document Type | PRE 14A |
| Amendment Flag | false |
| Entity Information [Line Items] | |
| Entity Registrant Name | MADRIGAL PHARMACEUTICALS, INC. |
| Entity Central Index Key | 0001157601 |
| Pay vs Performance Disclosure - USD ($) | 12 Months Ended | ||
| Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | |
| Pay vs Performance Disclosure [Table] | |||
| Pay vs Performance [Table Text Block] | PAY VERSUS PERFORMANCE The following table sets forth information concerning the compensation paid to our CEO and to our other NEOs compared to company performance for the years ended December 31, 2022, 2021 and 2020. The disclosure included in this section is prescribed by SEC rules and does not necessarily align with how the Company S-K Year Summary (1)(2) CAP to CEO (3) Average (1)(2) Average CAP to (3) Value of Initial Fixed GAAP Net (5) Company (4) Peer (4) 2022 $ 5,395,385 $ 38,419,031 $ 4,104,196 $ 29,641,483 $ 319 $ 111 $ (295,250 ) 2021 5,318,389 1,210,321 4,329,137 1,288,114 93 125 (241,846 ) 2020 4,535,446 6,480,322 3,677,403 5,646,095 122 126 (202,244 ) (1) For each year shown, the CEO was Paul A. Friedman. For 2022, the other NEOs were Rebecca Taub, M.D., Brian Lynch, Remy Sukhija, and Alex Howarth. For 2021, the other NEOs were Rebecca Taub, M.D., Brian Lynch, Remy Sukhija, Alex Howarth, and Marc Schneebaum. For 2020, the other NEOs were Rebecca Taub, M.D., Brian Lynch, Remy Sukhija and Marc Schneebaum. (2) The values reflected in this column reflect the “Total” compensation set forth in the Summary Compensation Table (“SCT”) on p. 34. See the footnotes to the SCT for further detail regarding the amounts in this column. (3) CAP is defined by the SEC and is computed in accordance with SEC rules by subtracting the amounts in the “Stock Awards” (as applicable) and “Option Awards” column of the SCT for each year from the “Total” column of the SCT and then: (i) adding the fair value as of the end of the reported year of all awards granted during the reporting year that are outstanding and unvested as of the end of the reporting year; (ii) adding the amount equal t o the change a ustments made CEO SCT Total Comp Minus SCT Equity Plus Year-End Plus Change in Fair Value Plus Change in Fair Value Equals CAP 2022 $ 5,395,385 $ (4,239,900 ) $ 18,078,963 $ 9,291,946 $ 9,892,637 $ 38,419,031 2021 5,318,389 (4,267,500 ) 2,696,917 (1,228,699 ) (1,308,786 ) 1,210,321 2020 4,535,446 (3,468,500 ) 4,187,875 584,964 640,537 6,480,322 Other NEOs (Average) SCT Total Minus SCT Equity Plus Year-End Plus Change in Fair Plus Change in Fair Equals CAP 2022 $ 4,104,196 $ (3,292,689 ) $ 14,322,661 $ 8,017,461 $ 6,489,853 $ 29,641,483 2021 4,329,137 (3,558,540 ) 1,814,098 (646,123 ) (650,457 ) 1,288,114 2020 3,677,403 (2,936,490 ) 3,343,083 1,291,002 271,097 5,646,095 (4) Reflects the cumulative TSR of the Company and the Nasdaq Biotechnology Index for the year ended December 31, 2020, the two-years (5) Amounts in thousands. | ||
| Named Executive Officers, Footnote [Text Block] | For 2022, the other NEOs were Rebecca Taub, M.D., Brian Lynch, Remy Sukhija, and Alex Howarth. | For 2021, the other NEOs were Rebecca Taub, M.D., Brian Lynch, Remy Sukhija, Alex Howarth, and Marc Schneebaum. | For 2020, the other NEOs were Rebecca Taub, M.D., Brian Lynch, Remy Sukhija and Marc Schneebaum. |
| Peer Group Issuers, Footnote [Text Block] | Reflects the cumulative TSR of the Company and the Nasdaq Biotechnology Index for the year ended December 31, 2020, the two-years | ||
| PEO Total Compensation Amount | $ 5,395,385 | $ 5,318,389 | $ 4,535,446 |
| PEO Actually Paid Compensation Amount | $ 38,419,031 | 1,210,321 | 6,480,322 |
| Adjustment To PEO Compensation, Footnote [Text Block] | CEO SCT Total Comp Minus SCT Equity Plus Year-End Plus Change in Fair Value Plus Change in Fair Value Equals CAP 2022 $ 5,395,385 $ (4,239,900 ) $ 18,078,963 $ 9,291,946 $ 9,892,637 $ 38,419,031 2021 5,318,389 (4,267,500 ) 2,696,917 (1,228,699 ) (1,308,786 ) 1,210,321 2020 4,535,446 (3,468,500 ) 4,187,875 584,964 640,537 6,480,322 | ||
| Non-PEO NEO Average Total Compensation Amount | $ 4,104,196 | 4,329,137 | 3,677,403 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 29,641,483 | 1,288,114 | 5,646,095 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | Other NEOs (Average) SCT Total Minus SCT Equity Plus Year-End Plus Change in Fair Plus Change in Fair Equals CAP 2022 $ 4,104,196 $ (3,292,689 ) $ 14,322,661 $ 8,017,461 $ 6,489,853 $ 29,641,483 2021 4,329,137 (3,558,540 ) 1,814,098 (646,123 ) (650,457 ) 1,288,114 2020 3,677,403 (2,936,490 ) 3,343,083 1,291,002 271,097 5,646,095 | ||
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | |||
| Compensation Actually Paid vs. Net Income [Text Block] | |||
| Total Shareholder Return Vs Peer Group [Text Block] | |||
| Tabular List [Table Text Block] | Tabular List of Financial Performance Measures Given the current pre-revenue | ||
| Total Shareholder Return Amount | $ 319 | 93 | 122 |
| Peer Group Total Shareholder Return Amount | 111 | 125 | 126 |
| Net Income (Loss) | $ (295,250,000) | (241,846,000) | (202,244,000) |
| PEO Name | Paul A. Friedman. | ||
| PEO [Member] | SCT Equity Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | $ (4,239,900) | (4,267,500) | (3,468,500) |
| PEO [Member] | Year End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 18,078,963 | 2,696,917 | 4,187,875 |
| PEO [Member] | Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 9,291,946 | (1,228,699) | 584,964 |
| PEO [Member] | Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 9,892,637 | (1,308,786) | 640,537 |
| Non-PEO NEO [Member] | SCT Equity Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (3,292,689) | (3,558,540) | (2,936,490) |
| Non-PEO NEO [Member] | Year End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 14,322,661 | 1,814,098 | 3,343,083 |
| Non-PEO NEO [Member] | Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 8,017,461 | (646,123) | 1,291,002 |
| Non-PEO NEO [Member] | Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | $ 6,489,853 | $ (650,457) | $ 271,097 |
