Amortized cost, gross unrealized gains and losses, approximate fair value, weighted average yield and contractual maturities of investment securities held-to-maturity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 124,372	$ 125,383	$ 142,106
Gross Unrealized Gains	1,131	825	7,308
Gross Unrealized Losses	674	954	1,598
Fair Value	124,829	125,254	147,816
Weighted Average Yield	4.28%	4.28%	3.54%
US Treasury Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	24,734
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	24,734
Weighted Average Yield	0.00%	0.00%	0.02%
US Treasury Securities [Member] | One Year From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	24,734
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	24,734
Weighted Average Yield	0.00%	0.00%	0.02%
US Treasury Securities [Member] | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	0
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	0
Weighted Average Yield	0.00%	0.00%	0.00%
US Treasury Securities [Member] | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	0
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	0
Weighted Average Yield	0.00%	0.00%	0.00%
US Treasury Securities [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	0
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	0
Weighted Average Yield	0.00%	0.00%	0.00%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	160	170
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	9	9
Fair Value	0	151	161
Weighted Average Yield	0.00%	5.45%	5.45%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member] | One Year From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	0
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	0
Weighted Average Yield	0.00%	0.00%	0.00%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member] | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	0
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	0
Weighted Average Yield	0.00%	0.00%	0.00%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member] | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	0
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	0
Weighted Average Yield	0.00%	0.00%	0.00%
Collateralized Mortgage Obligations Issued By Private Enterprise [Member] | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	160	170
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	9	9
Fair Value	0	151	161
Weighted Average Yield	0.00%	5.45%	5.45%
Other
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	26,500	26,250	26,500
Gross Unrealized Gains	29	83	133
Gross Unrealized Losses	0	0	0
Fair Value	26,529	26,333	26,633
Weighted Average Yield	3.39%	3.41%	3.35%
Other | One Year From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	1,250
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	1,250
Weighted Average Yield	0.00%	0.00%	0.96%
Other | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	26,500	26,250	25,250
Gross Unrealized Gains	29	83	133
Gross Unrealized Losses	0	0	0
Fair Value	26,529	26,333	25,383
Weighted Average Yield	3.39%	3.41%	3.47%
Other | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	0
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	0
Weighted Average Yield	0.00%	0.00%	0.00%
Other | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0	0	0
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Fair Value	0	0	0
Weighted Average Yield	0.00%	0.00%	0.00%
US Government Sponsored Enterprises Debt Securities Member
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0		0
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Fair Value	0		0
Weighted Average Yield	0.00%		0.00%
US Government Sponsored Enterprises Debt Securities Member | One Year From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0		0
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Fair Value	0		0
Weighted Average Yield	0.00%		0.00%
US Government Sponsored Enterprises Debt Securities Member | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0		0
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Fair Value	0		0
Weighted Average Yield	0.00%		0.00%
US Government Sponsored Enterprises Debt Securities Member | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0		0
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Fair Value	0		0
Weighted Average Yield	0.00%		0.00%
US Government Sponsored Enterprises Debt Securities Member | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0		0
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Fair Value	0		0
Weighted Average Yield	0.00%		0.00%
Obligations of Puerto Rico, States and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	97,717	98,973	90,702
Gross Unrealized Gains	1,096	742	7,175
Gross Unrealized Losses	674	945	1,589
Fair Value	98,139	98,770	96,288
Weighted Average Yield	4.52%	4.51%	4.55%
Obligations of Puerto Rico, States and political subdivisions | One Year From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	7,375	7,275	2,235
Gross Unrealized Gains	29	6	30
Gross Unrealized Losses	0	0	0
Fair Value	7,404	7,281	2,265
Weighted Average Yield	2.31%	2.24%	5.56%
Obligations of Puerto Rico, States and political subdivisions | More Than One And Within Five Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	11,649	11,174	15,973
Gross Unrealized Gains	556	430	356
Gross Unrealized Losses	0	0	0
Fair Value	12,205	11,604	16,329
Weighted Average Yield	5.83%	5.80%	4.19%
Obligations of Puerto Rico, States and political subdivisions | More Than Five And Within Ten Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	19,302	18,512	18,340
Gross Unrealized Gains	395	266	94
Gross Unrealized Losses	51	90	264
Fair Value	19,646	18,688	18,170
Weighted Average Yield	6.00%	5.99%	5.97%
Obligations of Puerto Rico, States and political subdivisions | More Than Ten Years From Balance Sheet Date [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	59,391	62,012	54,154
Gross Unrealized Gains	116	40	6,695
Gross Unrealized Losses	623	855	1,325
Fair Value	$ 58,884	$ 61,197	$ 59,524
Weighted Average Yield	4.05%	4.11%	4.13%