| Document and Entity Information Document | Dec. 18, 2020 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Title of 12(b) Security | Common Stock $0.01 par value |
| Document Period End Date | Dec. 18, 2020 |
| Entity Registrant Name | PRA Health Sciences, Inc. |
| Entity Central Index Key | 0001613859 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-36732 |
| Entity Tax Identification Number | 46-3640387 |
| Entity Address, Address Line One | 4130 ParkLake Avenue |
| Entity Address, Address Line Two | Suite 400 |
| Entity Address, City or Town | Raleigh |
| Entity Address, State or Province | NC |
| Entity Address, Postal Zip Code | 27612 |
| City Area Code | 919 |
| Local Phone Number | 786-8200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Trading Symbol | PRAH |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
