Borrowed Funds (Details Textual) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended	0 Months Ended	6 Months Ended		6 Months Ended			6 Months Ended								6 Months Ended		6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Jul. 23, 2008 ESB Capital Trust II (Trust II) [Member]	Jun. 30, 2012 ESB Capital Trust II (Trust II) [Member]	Apr. 10, 2003 ESB Capital Trust II (Trust II) [Member]	Jun. 30, 2012 ESB Capital Trust IV (Trust IV) [Member]	Jun. 30, 2012 ESB Statutory Trust (Trust III) [Member]	Dec. 17, 2003 ESB Statutory Trust (Trust III) [Member]	Jun. 30, 2012 Structured advances [Member]	Jun. 30, 2012 Repurchase agreements [Member]	Dec. 31, 2011 Repurchase agreements [Member]	Feb. 10, 2005 Fixed rate [Member] ESB Capital Trust IV (Trust IV) [Member]	Jun. 30, 2012 Variable rate [Member] ESB Capital Trust II (Trust II) [Member]	Apr. 10, 2003 Variable rate [Member] ESB Capital Trust II (Trust II) [Member]	Jun. 30, 2012 Variable rate [Member] ESB Statutory Trust (Trust III) [Member]	Dec. 17, 2003 Variable rate [Member] ESB Statutory Trust (Trust III) [Member]	Jun. 30, 2012 Structured REPOs [Member]	Dec. 31, 2011 Structured REPOs [Member]	Jun. 30, 2012 Citigroup [Member]	Dec. 31, 2011 Citigroup [Member]	Jun. 30, 2012 Barclays Capital [Member]	Dec. 31, 2011 Barclays Capital [Member]	Jun. 30, 2012 Credit Suisse [Member]	Dec. 31, 2011 Credit Suisse [Member]	Jun. 30, 2012 PNC Bank [Member]	Dec. 31, 2011 PNC Bank [Member]	Jun. 30, 2012 Morgan Stanley [Member]	Dec. 31, 2011 Morgan Stanley [Member]
Borrowed Funds (Textual) [Abstract]
FHLB advances	$ 191,599,000	$ 191,599,000	$ 207,355,000							$ 191,600,000	$ 318,000,000	$ 343,000,000
Structured advances										10,000,000
Structured REPO's											318,000,000							10,000,000
Period of fixed interest rate										4 years	5 years							4 years
Debt instrument variable rates basis										The Company also has $50.0 million in structured advances with imbedded caps at various strike rates based on the 3 month LIBOR rate.
Repurchase agreements with flexible interest rates																		30,000,000
REPO interest rate term																		3.75% based on the 3 month LIBOR rate
Repurchase agreements with fixed interest rate																		25,000,000
Securities available for sale, cost	1,107,595,000	1,107,595,000	1,091,497,000															352,700,000	375,000,000
REPO's with other banks																				135,000,000	145,000,000	60,000,000	70,000,000	93,000,000	93,000,000	0	5,000,000	30,000,000	30,000,000
Risk related to repurchase agreement amount																				18,100,000		8,600,000		11,500,000				4,100,000
Weighted average maturity																				21 months		33 months		25 months				19 months
Preferred securities													35,000,000		10,000,000		5,000,000
Liquidation preference per share						$ 1,000			$ 1,000
Redeemed preferred securities				5,000,000			1,100,000
Purchase of common securities					310,000,000		1,100,000	155,000,000
Proceeds from bank loan				14,000,000
Loans Payable					9,000,000
Interest rate					5.55%
Subordinated debt							36,100,000							10,300,000		5,200,000
Maturity date of subordinated debt					Apr. 24, 2033		Feb. 10, 2035	Dec. 17, 2033
Preferred securities fixed interest rate							6.03% for six years
Preferred securities variable interest rate					LIBOR plus 3.25%		Three month LIBOR plus 1.82%	LIBOR Index plus 2.95%
Maturity year of preferred securities							30 years
Maturity date of subordinated debt start date range					Apr. 24, 2008		Feb. 10, 2011	Dec. 17, 2008
Maturity date of subordinated debt end date range					Apr. 24, 2033		Feb. 10, 2035	Dec. 17, 2033
Borrowed Funds (Additional Textual) [Abstract]
Notional amount of imbedded caps	50,000,000	50,000,000
Market value of the securities	378,800,000	378,800,000	402,100,000
Repurchase agreements, maturities	Greater than 90 days		Greater than 90 days
Average borrowings under REPO		326,300,000
Maximum month-end outstanding amount		$ 343,000,000
Subordinated debt redemption description		the Company may redeem in whole, but not in part, the subordinated debt at any time within 90 days following the occurrence of such event
Libor Rate		3 months