Leases - Schedule of Supplemental Balance Sheet and Other Information Related to Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Operating Leases:
Right-of-use assets	$ 194,484	$ 210,398
Lease liabilities:
Current	53,997	54,133
Long-term	164,754	182,467
Total operating lease liabilities	218,751	236,600
Finance Leases:
Other noncurrent assets	3,414	3,363
Accrued expenses and other current liabilities	$ 1,598	$ 1,461
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	psn:AccruedExpensesAndOtherCurrentLiabilities	psn:AccruedExpensesAndOtherCurrentLiabilities
Other long-term liabilities	$ 1,618	$ 1,733
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other long-term liabilities	Other long-term liabilities
Weighted Average Remaining Lease Term:
Operating leases	4 years 8 months 12 days	5 years
Finance leases	2 years 6 months	3 years
Weighted Average Discount Rate:
Operating leases	3.60%	3.70%
Finance leases	3.00%	3.80%