Note Allowance for loan losses (Activity in Allowance for Loan Losses Related to ASC 310-30 Acquired Loans) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	$ 569,348	$ 623,426
Provision (reversal) for loan losses	41,825	71,063
Charge-offs	(79,841)	(67,816)
Balance at end of period	550,628	640,578
ASC Subtopic 310-30
Financing Receivable, Allowance for Credit Losses
Balance at beginning of period	122,135	119,505
Provision (reversal) for loan losses	7,726	37,335
Charge-offs	(5,714)	(10,720)
Balance at end of period	$ 124,147	$ 146,120