Loans and Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable
Net deferred loan origination fees	$ 36,800	$ 30,200
Net discount	89,300	136,800
Deposit liabilities reclassified as loans receivable	7,700	9,200
Loans with carrying value pledged to secure public deposits and other borrowings	8,600,000	7,600,000
Sabadell United | Non-US
Accounts, Notes, Loans and Financing Receivable
Covered loans acquired	182,400	202,600
TDRs Occurring during the Period | TDRs
Accounts, Notes, Loans and Financing Receivable
TDRs during period	57,874	53,171	$ 70,459
TDRs during period on accrual status	25,100	31,500	46,300
TDRs during period on non-accrual status	32,800	21,700	$ 24,200
Acquired Loans
Accounts, Notes, Loans and Financing Receivable
Net discount	$ 56,400	$ 81,600