Marketable Securities - Summary of Marketable Securities (Detail) - EUR (€) € in Thousands | Jun. 30, 2021 | Dec. 31, 2020 |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Non-current financial assets available-for-sale | € 90,693 | € 115,280 |
Current financial assets available-for-sale | 166,094 | 134,278 |
Financial assets at amortised cost, class [member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 256,787 | 249,558 |
Non-current financial assets available-for-sale | 90,693 | 115,280 |
Current financial assets available-for-sale | 166,094 | 134,278 |
Financial assets | 256,787 | 249,558 |
Financial assets at amortised cost, class [member] | Prime [member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 6,398 | 7,716 |
Financial assets at amortised cost, class [member] | High grade [member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 127,690 | 142,339 |
Financial assets at amortised cost, class [member] | Upper Medium Grade [member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 119,785 | 99,503 |
Financial assets at amortised cost, class [member] | Lower Medium Grade [member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 2,914 | |
Financial assets at amortised cost, class [member] | Fixed interest rate [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 231,342 | 175,757 |
Financial assets at amortised cost, class [member] | Floating interest rate [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 16,613 | 16,975 |
Financial assets at amortised cost, class [member] | Zero Coupon [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 8,832 | 56,826 |
Financial assets at amortised cost, class [member] | US Treasury bills [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 0 | 46,243 |
Financial assets at amortised cost, class [member] | US Government bonds [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 85,049 | 62,088 |
Financial assets at amortised cost, class [member] | Commercial papers [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 8,832 | 10,583 |
Financial assets at amortised cost, class [member] | Corporate bonds [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 144,830 | 121,282 |
Financial assets at amortised cost, class [member] | Agency bonds [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 18,076 | 9,362 |
Financial assets at fair value, class [member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 256,693 | 249,530 |
Non-current financial assets available-for-sale | 90,623 | 115,277 |
Current financial assets available-for-sale | 166,070 | 134,253 |
Financial assets | 256,693 | 249,530 |
Financial assets at fair value, class [member] | Prime [member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 6,398 | 7,714 |
Financial assets at fair value, class [member] | High grade [member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 127,678 | 142,352 |
Financial assets at fair value, class [member] | Upper Medium Grade [member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 119,706 | 99,464 |
Financial assets at fair value, class [member] | Lower Medium Grade [member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 2,911 | |
Financial assets at fair value, class [member] | Fixed interest rate [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 231,249 | 175,732 |
Financial assets at fair value, class [member] | Floating interest rate [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 16,611 | 16,972 |
Financial assets at fair value, class [member] | Zero Coupon [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets | 8,833 | 56,826 |
Financial assets at fair value, class [member] | US Treasury bills [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 0 | 46,245 |
Financial assets at fair value, class [member] | US Government bonds [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 85,049 | 62,101 |
Financial assets at fair value, class [member] | Commercial papers [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 8,833 | 10,581 |
Financial assets at fair value, class [member] | Corporate bonds [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | 144,734 | 121,234 |
Financial assets at fair value, class [member] | Agency bonds [Member] | | |
Disclosure Detailed Information About Marketable Securities [Line Items] | | |
Financial assets available-for-sale | € 18,077 | € 9,369 |