Note Debt Securities Held-to-maturity (Debt securities held-to-maturity-Additional Information) (Detail) - USD ($) $ in Thousands	Jun. 30, 2018		Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 104,937	[1]	$ 107,019	[2]
Obligations of Puerto Rico, States and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	90,928		$ 92,754
Obligations of Puerto Rico, States and political subdivisions | Munis Payable From Real and Personal Property Taxes
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	47,000
Obligations of Puerto Rico, States and political subdivisions | Munis Not Guaranteed By Puerto Rico Central Government
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 44,000

[1] Includes $90.9 million pledged to secure public and trust deposits that the secured parties are not permitted to sell or repledge the collateral.

[2] Includes $92.8 million pledged to secure public and trust deposits that the secured parties are not permitted to sell or repledge the collateral.