Loss Sharing Agreements and FDIC Loss Share Receivable (Detail) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) acquisition	Sep. 30, 2016 USD ($) Business acquisition	Dec. 31, 2021 acquisition	Dec. 31, 2020 acquisition	Dec. 31, 2019 acquisition	Dec. 31, 2015 USD ($) acquisition	Dec. 31, 2014 USD ($) acquisition	Sep. 30, 2015 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%	95.00%
Loss Sharing Agreements and FDIC Loss Share Receivable [Line Items]
Number of acquisitions exceeding loan loss contractual threshold		3
Recovery period for covered assets		3 years
FDIC loss share receivables | $	$ 24,406	$ 24,406				$ 39,878	$ 69,627	$ 43,443
Excluding Single Family
Loss Sharing Agreements and FDIC Loss Share Receivable [Line Items]
Number of acquisitions exceeding loan loss contractual threshold	2					1	3
Forecast | Single Family
Loss Sharing Agreements and FDIC Loss Share Receivable [Line Items]
Number of acquisitions exceeding loan loss contractual threshold			2	1	3