Investment Securities - Summary of Continuous Unrealized Loss Position of Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Fair Value, Less Than 12 Months, Available-for-sale	$ 3,656	$ 615,765
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale	(58)	(2,844)
Fair Value, 12 Months or Longer, Available-for-sale	5,966	5,961
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale	(1)	(1)
Fair Value, Available-for-sale	9,622	621,726
Gross Unrealized Holding Losses, Available-for-sale	(59)	(2,845)
Fair Value, Less Than 12 Months, Held-to-maturity	92,467	425,374
Gross Unrealized Holding Losses, Less Than 12 Months, Held-to-maturity	(1,024)	(2,746)
Fair Value, 12 Months or Longer, Held-to-maturity	0	0
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity	0	0
Fair Value, Held-to-maturity	92,467	425,374
Gross Unrealized Holding Losses, Held-to-maturity	(1,024)	(2,746)
CMO's/REMIC's - Residential [Member]
Schedule of Investments [Line Items]
Fair Value, Less Than 12 Months, Available-for-sale	0	171,923
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale	0	(1,074)
Fair Value, 12 Months or Longer, Available-for-sale	0	0
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale	0	0
Fair Value, Available-for-sale	0	171,923
Gross Unrealized Holding Losses, Available-for-sale	0	(1,074)
Fair Value, Less Than 12 Months, Held-to-maturity	0	0
Gross Unrealized Holding Losses, Less Than 12 Months, Held-to-maturity	0	0
Fair Value, 12 Months or Longer, Held-to-maturity	0	0
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity	0	0
Fair Value, Held-to-maturity	0	0
Gross Unrealized Holding Losses, Held-to-maturity	0	0
Government Agency/GSEs [Member]
Schedule of Investments [Line Items]
Fair Value, Less Than 12 Months, Available-for-sale	0	5,745
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale	0	(7)
Fair Value, 12 Months or Longer, Available-for-sale	0	0
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale	0	0
Fair Value, Available-for-sale	0	5,745
Gross Unrealized Holding Losses, Available-for-sale	0	(7)
Fair Value, Less Than 12 Months, Held-to-maturity	0	84,495
Gross Unrealized Holding Losses, Less Than 12 Months, Held-to-maturity	0	(734)
Fair Value, 12 Months or Longer, Held-to-maturity	0	0
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity	0	0
Fair Value, Held-to-maturity	0	84,495
Gross Unrealized Holding Losses, Held-to-maturity	0	(734)
Residential Mortgage-backed Securities [Member]
Schedule of Investments [Line Items]
Fair Value, Less Than 12 Months, Available-for-sale	0	437,699
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale	0	(1,761)
Fair Value, 12 Months or Longer, Available-for-sale	0	0
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale	0	0
Fair Value, Available-for-sale	0	437,699
Gross Unrealized Holding Losses, Available-for-sale	0	(1,761)
Fair Value, Less Than 12 Months, Held-to-maturity	0	230,760
Gross Unrealized Holding Losses, Less Than 12 Months, Held-to-maturity	0	(1,293)
Fair Value, 12 Months or Longer, Held-to-maturity	0	0
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity	0	0
Fair Value, Held-to-maturity	0	230,760
Gross Unrealized Holding Losses, Held-to-maturity	0	(1,293)
Municipal Bonds [Member]
Schedule of Investments [Line Items]
Fair Value, Less Than 12 Months, Available-for-sale	3,656	398
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale	(58)	(2)
Fair Value, 12 Months or Longer, Available-for-sale	5,966	5,961
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale	(1)	(1)
Fair Value, Available-for-sale	9,622	6,359
Gross Unrealized Holding Losses, Available-for-sale	(59)	(3)
Fair Value, Less Than 12 Months, Held-to-maturity	92,467	110,119
Gross Unrealized Holding Losses, Less Than 12 Months, Held-to-maturity	(1,024)	(719)
Fair Value, 12 Months or Longer, Held-to-maturity	0	0
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity	0	0
Fair Value, Held-to-maturity	92,467	110,119
Gross Unrealized Holding Losses, Held-to-maturity	(1,024)	(719)
Other Securities [Member]
Schedule of Investments [Line Items]
Fair Value, Less Than 12 Months, Available-for-sale	0	0
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale	0	0
Fair Value, 12 Months or Longer, Available-for-sale	0	0
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale	0	0
Fair Value, Available-for-sale	0	0
Gross Unrealized Holding Losses, Available-for-sale	0	0
Fair Value, Less Than 12 Months, Held-to-maturity	0	0
Gross Unrealized Holding Losses, Less Than 12 Months, Held-to-maturity	0	0
Fair Value, 12 Months or Longer, Held-to-maturity	0	0
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity	0	0
Fair Value, Held-to-maturity	0	0
Gross Unrealized Holding Losses, Held-to-maturity	$ 0	$ 0

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

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