Subsequent Events (Details) (USD $)					3 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Integrity Bancshares, Inc. [Member] branch	Oct. 29, 2014 Integrity Bancshares, Inc. [Member] Subsequent Event [Member]	Jun. 30, 2015 Scenario, Forecast [Member] Integrity Bancshares, Inc. [Member]	Oct. 29, 2014 Minimum [Member] Integrity Bancshares, Inc. [Member] Subsequent Event [Member]	Oct. 29, 2014 Maximum [Member] Integrity Bancshares, Inc. [Member] Subsequent Event [Member]
Subsequent Event [Line Items]
Assets	$ 4,906,744,000	$ 4,533,190,000	$ 860,000,000
Number of branches			8
Price per share of Integrity common stock				$ 52.50
Shares of S&T issued per share of Integrity stock				2.0627
Percentage of Integrity common shares acquired in exchange for S&T common stock						80.00%
Percentage of Integrity common shares acquired for cash							20.00%
Value of transaction				$ 155,000,000
Period S&T intends to operate branches in markets served by Integrity					3 years