XML 26 R14.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Restrictions on Cash and Due from Bank Accounts | 12 Months Ended
--- | ---
Dec. 31, 2021
Cash and Cash Equivalents [Abstract] |
RESTRICTIONS ON CASH AND DUE FROM BANK ACCOUNTS | RESTRICTIONS ON CASH AND DUE FROM BANK ACCOUNTSThe Board of Governors of the Federal Reserve System, or the Federal Reserve, imposes certain reserve requirements on all depository institutions. These reserves are maintained in the form of vault cash or as an interest-bearing balance with the Federal Reserve. The required reserves averaged $0.0 million for 2021, $15.5 million for 2020 and $43.9 million for 2019. The decrease in the required reserve average from 2020 to 2021 was due to the Federal Reserve reducing the reserve requirement ratio to zero percent effective March 26, 2020.

X
- Definition Cash reserve requirement of the Federal Reserve. + References No definition available. + Details
Name: | stba_RestrictionsOnCashAndDueFromBankAccountsTextBlock
Namespace Prefix: | stba_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_CashAndCashEquivalentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration