Summary of Held-to-Maturity and Available-for-Sale Securities Having Continuous Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2015		Dec. 31, 2014
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity Securities, Total Unrealized Loss	$ 29,331	[1]	$ 49,664	[2]
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Fair Value	105,702		53,721
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Unrealized Loss	356		364
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Fair Value	4,997		20,625
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Unrealized Loss	2,448		2,099
Temporarily Impaired Available-for-Sale Securities, Total Fair Value	110,699		74,346
Temporarily Impaired Available-for-Sale Securities, Total Unrealized Loss	2,804		2,463
Debt Securities
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Fair Value	923,130		13,735
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Unrealized Loss	6,876		195
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Fair Value	1,201,558		2,587,594
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Unrealized Loss	22,455		49,469
Temporarily Impaired Held-to-Maturity Securities, Total Fair Value	2,124,688		2,601,329
Temporarily Impaired Held-to-Maturity Securities, Total Unrealized Loss	29,331		49,664
Debt Securities | Capital trust notes
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Fair Value	24,601
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Unrealized Loss	399
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Fair Value	20,710		25,019
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Unrealized Loss	15,501		11,168
Temporarily Impaired Held-to-Maturity Securities, Total Fair Value	45,311		25,019
Temporarily Impaired Held-to-Maturity Securities, Total Unrealized Loss	15,900		11,168
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Fair Value	1,968
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Unrealized Loss	32
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Fair Value	4,997		5,451
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Unrealized Loss	2,448		1,980
Temporarily Impaired Available-for-Sale Securities, Total Fair Value	6,965		5,451
Temporarily Impaired Available-for-Sale Securities, Total Unrealized Loss	2,480		1,980
Debt Securities | GSE debentures
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Fair Value	547,484
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Unrealized Loss	728
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Fair Value	1,176,949		2,204,399
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Unrealized Loss	6,840		32,920
Temporarily Impaired Held-to-Maturity Securities, Total Fair Value	1,724,433		2,204,399
Temporarily Impaired Held-to-Maturity Securities, Total Unrealized Loss	7,568		32,920
Debt Securities | GSE certificates
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Fair Value	299,019
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Unrealized Loss	4,608
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Fair Value	3,899		242,909
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Unrealized Loss	114		3,838
Temporarily Impaired Held-to-Maturity Securities, Total Fair Value	302,918		242,909
Temporarily Impaired Held-to-Maturity Securities, Total Unrealized Loss	4,722		3,838
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Fair Value	51,959
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Unrealized Loss	1
Temporarily Impaired Available-for-Sale Securities, Total Fair Value	51,959
Temporarily Impaired Available-for-Sale Securities, Total Unrealized Loss	1
Debt Securities | Municipal bonds
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Fair Value	42,083		13,735
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Unrealized Loss	1,084		195
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Fair Value			43,058
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Unrealized Loss			832
Temporarily Impaired Held-to-Maturity Securities, Total Fair Value	42,083		56,793
Temporarily Impaired Held-to-Maturity Securities, Total Unrealized Loss	1,084		1,027
Debt Securities | GSE CMOs
Schedule of Investments [Line Items]
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Fair Value	9,943
Temporarily Impaired Held-to-Maturity Securities, Less than Twelve Months Unrealized Loss	57
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Fair Value			72,209
Temporarily Impaired Held-to-Maturity Securities, Twelve Months or Longer Unrealized Loss			711
Temporarily Impaired Held-to-Maturity Securities, Total Fair Value	9,943		72,209
Temporarily Impaired Held-to-Maturity Securities, Total Unrealized Loss	57		711
Equity securities
Schedule of Investments [Line Items]
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Fair Value	51,775		53,721
Temporarily Impaired Available-for-Sale Securities, Less than Twelve Months Unrealized Loss	323		364
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Fair Value			15,174
Temporarily Impaired Available-for-Sale Securities, Twelve Months or Longer Unrealized Loss			119
Temporarily Impaired Available-for-Sale Securities, Total Fair Value	51,775		68,895
Temporarily Impaired Available-for-Sale Securities, Total Unrealized Loss	$ 323		$ 483

[1] Held-to-maturity securities are reported at a carrying amount equal to amortized cost less the non-credit portion of OTTI recorded in AOCL. At December 31, 2015, the non-credit portion of OTTI recorded in AOCL was $8.7 million (before taxes).

[2] Held-to-maturity securities are reported at a carrying amount equal to amortized cost less the non-credit portion of OTTI recorded in AOCL. At December 31, 2014, the non-credit portion of OTTI recorded in AOCL was $8.8 million (before taxes).