Note Commitments and Contingencies (Schedule of Direct Exposure to Puerto Rico Government by Maturity) (Detail) - PR Government Direct Exposure - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	$ 481,306	$ 483,580
From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	60
From Government Development Bank
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	3
From Public Corporation - Puerto Rico Highways And Transportation Authority
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	4
From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	481,239
Outstanding Balance
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	481,306	483,580
Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	60
Outstanding Balance | From Government Development Bank
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	3
Outstanding Balance | From Public Corporation - Puerto Rico Highways And Transportation Authority
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	4
Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	481,239
Loans Member | Outstanding Balance
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	434,434	434,493
Loans Member | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	0
Loans Member | Outstanding Balance | From Government Development Bank
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	0
Loans Member | Outstanding Balance | From Public Corporation - Puerto Rico Highways And Transportation Authority
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	0
Loans Member | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	434,434
Securities Investment Member | Outstanding Balance
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	46,872	$ 49,045
Securities Investment Member | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	60
Securities Investment Member | Outstanding Balance | From Government Development Bank
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	3
Securities Investment Member | Outstanding Balance | From Public Corporation - Puerto Rico Highways And Transportation Authority
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	4
Securities Investment Member | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	46,805
Within 1 year | From Government Development Bank
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	3
Within 1 year | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	12,899
Within 1 year | Outstanding Balance | From Government Development Bank
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	3
Within 1 year | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	12,899
Within 1 year | Loans Member | Outstanding Balance | From Government Development Bank
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	0
Within 1 year | Loans Member | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	9,454
Within 1 year | Securities Investment Member | Outstanding Balance | From Government Development Bank
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	3
Within 1 year | Securities Investment Member | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	3,445
After 1 and within 5 years | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	4
After 1 and within 5 years | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	212,564
After 1 and within 5 years | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	4
After 1 and within 5 years | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	212,564
After 1 and within 5 years | Loans Member | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	0
After 1 and within 5 years | Loans Member | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	196,369
After 1 and within 5 years | Securities Investment Member | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	4
After 1 and within 5 years | Securities Investment Member | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	16,195
After 5 to 10 years | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	9
After 5 to 10 years | From Public Corporation - Puerto Rico Highways And Transportation Authority
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	4
After 5 to 10 years | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	132,713
After 5 to 10 years | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	9
After 5 to 10 years | Outstanding Balance | From Public Corporation - Puerto Rico Highways And Transportation Authority
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	4
After 5 to 10 years | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	132,713
After 5 to 10 years | Loans Member | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	0
After 5 to 10 years | Loans Member | Outstanding Balance | From Public Corporation - Puerto Rico Highways And Transportation Authority
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	0
After 5 to 10 years | Loans Member | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	106,573
After 5 to 10 years | Securities Investment Member | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	9
After 5 to 10 years | Securities Investment Member | Outstanding Balance | From Public Corporation - Puerto Rico Highways And Transportation Authority
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	4
After 5 to 10 years | Securities Investment Member | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	26,140
After 10 years | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	47
After 10 years | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Total concentration of risk	123,063
After 10 years | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	47
After 10 years | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	123,063
After 10 years | Loans Member | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	0
After 10 years | Loans Member | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	122,038
After 10 years | Securities Investment Member | Outstanding Balance | From PR Central Government
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	47
After 10 years | Securities Investment Member | Outstanding Balance | From Municipalities
Direct Exposure To The Puerto Rico Government By Maturity [Line Items]
Outstanding concentration of risk	$ 1,025