Note Loans - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Assets Obtained As Proceeds	$ 140,657	$ 177,090
Loans and Leases Receivable, Gross, Carrying Amount, Covered	514,611		$ 517,274
Mortgage loans related to buy-back option program	24,224,793		24,423,427
Buy back option program
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage loans related to buy-back option program	535,000		840,000
GNMA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Assets Obtained As Proceeds	112,000	147,000
FNMA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Assets Obtained As Proceeds	26,000	28,000
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential Mortgage Loans Sold	10,000	28,000
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of Loans	51,000	42,000
Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of Loans	156,000	136,000
Leasing | Corporate Joint Venture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of Loans		$ 2
Westernbank Puerto Rico | ASC Subtopic 310-30
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding principal balance of SOP loans	1,900,000		1,900,000
Westernbank Puerto Rico | ASC Subtopic 310-20
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	10,000		10,000
SOP Other Loans Acquired | ASC Subtopic 310-30
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding principal balance of SOP loans	$ 552,000		$ 556,000