Note Debt Securities Held-to-maturity (HTM debt securities in a continuous unrealized loss position) (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Held-to-maturity [Line Items]
Less than 12 months Fair Value	$ 17,359	$ 0
Less than 12 months Gross Unrealized Losses	219	0
12 months or more Fair Value	14,926	36,439
12 months or more Gross Unrealized Losses	584	13,356
Total Fair Value	32,285	36,439
Total Gross Unrealized Losses	803	13,356
Obligations of Puerto Rico, States and political subdivisions
Debt Securities, Held-to-maturity [Line Items]
Less than 12 months Fair Value	17,359	0
Less than 12 months Gross Unrealized Losses	219	0
12 months or more Fair Value	14,431	35,696
12 months or more Gross Unrealized Losses	579	13,349
Total Fair Value	31,790	35,696
Total Gross Unrealized Losses	798	13,349
Other
Debt Securities, Held-to-maturity [Line Items]
Less than 12 months Fair Value	0	0
Less than 12 months Gross Unrealized Losses	0	0
12 months or more Fair Value	495	743
12 months or more Gross Unrealized Losses	5	7
Total Fair Value	495	743
Total Gross Unrealized Losses	$ 5	$ 7