Summary of Held-to-Maturity and Available-for-Sale Securities Having Continuous Unrealized Loss Position (Detail) (USD $)	Sep. 30, 2012		Dec. 31, 2011
Schedule of Investments [Line Items]
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Fair Value	$ 18,472,000		$ 40,160,000
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Unrealized Loss	331,000		1,677,000
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Fair Value	36,185,000		36,474,000
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Unrealized Loss	5,202,000		8,506,000
Temporarily Impaired Available-for-Sale Securities, Total Fair Value	54,657,000		76,634,000
Temporarily Impaired Available-for-Sale Securities, Total Unrealized Loss	5,533,000		10,183,000
Debt Securities
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity, Less than Twelve Months Fair Value	14,956,000		68,559,000
Temporarily Impaired Held-to-Maturity, Less than Twelve Months Unrealized Loss	26,000		201,000
Temporarily Impaired Held-to-Maturity, Twelve Months or Longer Fair Value	55,373,000		68,570,000
Temporarily Impaired Held-to-Maturity, Twelve Months or Longer Unrealized Loss	15,767,000		19,814,000
Temporarily Impaired Held-to-Maturity, Total Fair Value	70,329,000		137,129,000
Temporarily Impaired Held-to-Maturity, Total Unrealized Loss	15,793,000		20,015,000
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Fair Value	18,472,000		39,376,000
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Unrealized Loss	331,000		1,637,000
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Fair Value	6,518,000		9,823,000
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Unrealized Loss	4,009,000		4,330,000
Temporarily Impaired Available-for-Sale Securities, Total Fair Value	24,990,000		49,199,000
Temporarily Impaired Available-for-Sale Securities, Total Unrealized Loss	4,340,000		5,967,000
Debt Securities | GSE certificates
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity, Less than Twelve Months Fair Value	14,956,000
Temporarily Impaired Held-to-Maturity, Less than Twelve Months Unrealized Loss	26,000
Temporarily Impaired Held-to-Maturity, Total Fair Value	14,956,000
Temporarily Impaired Held-to-Maturity, Total Unrealized Loss	26,000
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Fair Value	371,000		181,000
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Unrealized Loss	6,000		9,000
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Fair Value			13,000
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Unrealized Loss			1,000
Temporarily Impaired Available-for-Sale Securities, Total Fair Value	371,000		194,000
Temporarily Impaired Available-for-Sale Securities, Total Unrealized Loss	6,000		10,000
Debt Securities | Private label CMOs
Schedule of Investments [Line Items]
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Fair Value	18,101,000		24,041,000
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Unrealized Loss	325,000		1,265,000
Temporarily Impaired Available-for-Sale Securities, Total Fair Value	18,101,000		24,041,000
Temporarily Impaired Available-for-Sale Securities, Total Unrealized Loss	325,000		1,265,000
Debt Securities | Capital trust notes
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity, Less than Twelve Months Fair Value			971,000
Temporarily Impaired Held-to-Maturity, Less than Twelve Months Unrealized Loss			43,000
Temporarily Impaired Held-to-Maturity, Twelve Months or Longer Fair Value	55,373,000		68,570,000
Temporarily Impaired Held-to-Maturity, Twelve Months or Longer Unrealized Loss	15,767,000		19,814,000
Temporarily Impaired Held-to-Maturity, Total Fair Value	55,373,000		69,541,000
Temporarily Impaired Held-to-Maturity, Total Unrealized Loss	15,767,000		19,857,000
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Fair Value			15,154,000
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Unrealized Loss			363,000
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Fair Value	6,518,000		9,810,000
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Unrealized Loss	4,009,000		4,329,000
Temporarily Impaired Available-for-Sale Securities, Total Fair Value	6,518,000		24,964,000
Temporarily Impaired Available-for-Sale Securities, Total Unrealized Loss	4,009,000		4,692,000
Debt Securities | Corporate bonds
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity, Less than Twelve Months Fair Value			4,987,000
Temporarily Impaired Held-to-Maturity, Less than Twelve Months Unrealized Loss			12,000
Temporarily Impaired Held-to-Maturity, Total Fair Value			4,987,000
Temporarily Impaired Held-to-Maturity, Total Unrealized Loss			12,000
Debt Securities | GSE debentures
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity, Less than Twelve Months Fair Value			62,601,000
Temporarily Impaired Held-to-Maturity, Less than Twelve Months Unrealized Loss			146,000
Temporarily Impaired Held-to-Maturity, Total Fair Value			62,601,000
Temporarily Impaired Held-to-Maturity, Total Unrealized Loss			146,000
Equity Securities
Schedule of Investments [Line Items]
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Fair Value			784,000
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Unrealized Loss			40,000
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Fair Value	29,667,000		26,651,000
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Unrealized Loss	1,193,000	[1]	4,176,000
Temporarily Impaired Available-for-Sale Securities, Total Fair Value	29,667,000		27,435,000
Temporarily Impaired Available-for-Sale Securities, Total Unrealized Loss	$ 1,193,000		$ 4,216,000

[1] The twelve months or longer unrealized losses on equity securities of $1.2 million at September 30, 2012 relate to available-for-sale equity securities that consisted of a large cap equity fund and investments in certain financial institutions at that date. The principal balance of the large cap equity fund was $29.1 million and the twelve months or longer unrealized loss was $556,000. The principal balance of investments in financial institutions totaled $1.7 million and the twelve months or longer unrealized loss was $623,000.