Loans (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable
Net deferred loan origination fees	$ 30,800		$ 30,200
Net discount	130,100		136,800
Deposit liabilities reclassified as loans receivable	6,400		9,200
Loans with carrying value pledged to secure public deposits and other borrowings	7,800,000		7,600,000
Loans acquired with no evidence of deteriorated credit quality	550		3,143
Acquired Loans
Accounts, Notes, Loans and Financing Receivable
Net discount	79,000		81,600
Sabadell United | Non-US
Accounts, Notes, Loans and Financing Receivable
Covered loans acquired	205,200		$ 202,600
TDRs Occurring during the Period | TDRs
Accounts, Notes, Loans and Financing Receivable
TDRs during period	31,429	$ 27,200
TDRs during period on accrual status	16,500	12,900
TDRs during period on non-accrual status	$ 14,900	$ 14,300