Borrowed Funds - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	0 Months Ended	6 Months Ended		6 Months Ended			6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Trust IV Preferred Securities [Member]	Feb. 10, 2005 ESB Capital Trust IV (Trust IV) [Member]	Jun. 30, 2014 ESB Capital Trust IV (Trust IV) [Member]	Feb. 10, 2005 ESB Capital Trust IV (Trust IV) [Member]	Jun. 30, 2014 Structured Repurchase Agreement with Imbedded Cap [Member]	Jun. 30, 2014 Structured REPOs [Member]	Dec. 31, 2013 Structured REPOs [Member]	Jun. 30, 2014 Citigroup [Member]	Dec. 31, 2013 Citigroup [Member]	Jun. 30, 2014 Barclays Capital [Member]	Dec. 31, 2013 Barclays Capital [Member]	Jun. 30, 2014 Credit Suisse [Member]	Dec. 31, 2013 Credit Suisse [Member]	Jun. 30, 2014 Morgan Stanley [Member]	Dec. 31, 2013 Morgan Stanley [Member]
Debt Instrument [Line Items]
REPOs with other banks	$ 108,000,000	$ 108,000,000									$ 25,000,000	$ 45,000,000	$ 30,000,000	$ 30,000,000	$ 43,000,000	$ 43,000,000	$ 10,000,000	$ 20,000,000
LIBOR rate		3 months							3 months
Repurchase agreements with fixed interest rate								10,000,000	25,000,000
Debt instrument variable rates basis									10.0 million structured REPO with an imbedded cap at a strike rate of 3.00% based on the 3 month LIBOR rate
Strike rate of imbedded caps									3.00%
REPO interest rate term									3.00% based on the 3 month LIBOR rate
Market value of the securities	129,900,000	129,900,000	168,800,000
Securities available for sale, cost	1,065,482,000	1,065,482,000	1,051,311,000						122,000,000	160,400,000
Repurchase agreements, maturities		Greater than 90 days	Greater than 90 days
Risk related to repurchase agreement amount											2,300,000		6,300,000		10,700,000		81,000,000,000
Weighted average maturity											34 months		37 months		32 months		1 month
Average borrowings under REPO	114,700,000	123,000,000
Maximum month-end outstanding amount	118,000,000	138,000,000
Preferred securities							35,000,000
Purchase of common securities					1,100,000
Preferred securities fixed interest rate						6.03% for six years
Preferred securities variable interest rate						Three month LIBOR plus 1.82%
Maturity year of preferred securities						30 years
Fixed interest rate				6.03%
Preferred securities interest rate				1.82%
Preferred securities maturity period		6 years
Subordinated debt						$ 36,100,000
Maturity date of subordinated debt start date range						Feb. 10, 2011
Maturity date of subordinated debt end date range						Feb. 10, 2035
Maturity of redemption of subordinated debt				90 days