Note Debt Securities Held-to-maturity (HTM debt securities in a continuous unrealized loss position) (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Securities, Held-to-maturity [Line Items]
Less than 12 months Fair Value	$ 7,486	$ 0
Less than 12 months Gross Unrealized Losses	19	0
12 months or more Fair Value	30,017	36,439
12 months or more Gross Unrealized Losses	1,568	13,356
Total Fair Value	37,503	36,439
Total Gross Unrealized Losses	1,587	13,356
Obligations of Puerto Rico, States and political subdivisions
Debt Securities, Held-to-maturity [Line Items]
Less than 12 months Fair Value	7,236	0
Less than 12 months Gross Unrealized Losses	19	0
12 months or more Fair Value	29,524	35,696
12 months or more Gross Unrealized Losses	1,561	13,349
Total Fair Value	36,760	35,696
Total Gross Unrealized Losses	1,580	13,349
Other
Debt Securities, Held-to-maturity [Line Items]
Less than 12 months Fair Value	250	0
Less than 12 months Gross Unrealized Losses	0	0
12 months or more Fair Value	493	743
12 months or more Gross Unrealized Losses	7	7
Total Fair Value	743	743
Total Gross Unrealized Losses	$ 7	$ 7