Loss Sharing Agreements and FDIC Loss Share Receivable (Detail) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) Business acquisition	Sep. 30, 2014 USD ($)	Dec. 31, 2021 acquisition	Dec. 31, 2020 acquisition	Dec. 31, 2019 acquisition	Dec. 31, 2016 acquisition	Dec. 31, 2015 acquisition	Dec. 31, 2014 USD ($) acquisition	Dec. 31, 2013 USD ($)
Loss Sharing Agreements and FDIC Loss Share Receivable [Abstract]
Number of acquisitions | Business	6
Percentage of covered loan and foreclosed real estate losses	80.00%
Percentage of losses, that exceed contractual thresholds, that are covered	95.00%
Number of acquisitions exceeding loan loss contractual threshold	3
Loss Sharing Agreements and FDIC Loss Share Receivable [Line Items]
Recovery period for covered assets	3 years
FDIC loss share receivables | $	$ 43,443	$ 94,712						$ 69,627	$ 162,312
Impairment | $	$ 0	$ 5,097
Excluding Single Family
Loss Sharing Agreements and FDIC Loss Share Receivable [Line Items]
Number of acquisitions where FDIC loan loss reimbursable period is ending								3
Excluding Single Family | Forecast
Loss Sharing Agreements and FDIC Loss Share Receivable [Line Items]
Number of acquisitions where FDIC loan loss reimbursable period is ending						2	1
Single Family | Forecast
Loss Sharing Agreements and FDIC Loss Share Receivable [Line Items]
Number of acquisitions where FDIC loan loss reimbursable period is ending			2	1	3