Summary of Portfolio of Securities Held to Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 7,679,472	[1]	$ 4,505,831	[2]
Carrying Amount	7,670,282	[1]	4,484,262	[2]
Gross Unrealized Gain	80,203	[1]	235,700	[2]
Gross Unrealized Loss	305,241	[1]	14,002	[2]
Fair Value	7,445,244	[1]	4,705,960	[2]
Mortgage-Related Securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	4,407,987		3,155,217
Carrying Amount	4,407,987		3,155,217
Gross Unrealized Gain	59,475		192,624
Gross Unrealized Loss	83,800		5
Fair Value	4,383,662		3,347,836
Mortgage-Related Securities | GSE certificates
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	2,529,102		1,253,769
Carrying Amount	2,529,102		1,253,769
Gross Unrealized Gain	30,145		87,860
Gross Unrealized Loss	61,280		5
Fair Value	2,497,967		1,341,624
Mortgage-Related Securities | GSE CMOs
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,878,885		1,898,228
Carrying Amount	1,878,885		1,898,228
Gross Unrealized Gain	29,330		104,764
Gross Unrealized Loss	22,520
Fair Value	1,885,695		2,002,992
Mortgage-Related Securities | Other mortgage-related securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost			3,220
Carrying Amount			3,220
Fair Value			3,220
Other Securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,271,485		1,350,614
Carrying Amount	3,262,295		1,329,045
Gross Unrealized Gain	20,728		43,076
Gross Unrealized Loss	221,441		13,997
Fair Value	3,061,582		1,358,124
Other Securities | GSE debentures
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,053,253		1,129,618
Carrying Amount	3,053,253		1,129,618
Gross Unrealized Gain	6,512		15,739
Gross Unrealized Loss	208,506
Fair Value	2,851,259		1,145,357
Other Securities | Corporate bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	72,899		72,501
Carrying Amount	72,899		72,501
Gross Unrealized Gain	11,063		12,504
Fair Value	83,962		85,005
Other Securities | Municipal bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	60,462		16,982
Carrying Amount	60,462		16,982
Gross Unrealized Gain	19		245
Gross Unrealized Loss	3,849
Fair Value	56,632		17,227
Other Securities | Capital trust notes
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	84,871		131,513
Carrying Amount	75,681		109,944
Gross Unrealized Gain	3,134		14,588
Gross Unrealized Loss	9,086		13,997
Fair Value	$ 69,729		$ 110,535

[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, 2013, the non-credit portion of OTTI recorded in AOCL was $9.2 million (before taxes).

[2] At December 31, 2012, the non-credit portion of OTTI recorded in AOCL was $21.6 million (before taxes).