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Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020
Investment Securities [Line Items] |  |
Amortized Cost | $ 1,045,579 | $ 805,515
Gross Unrealized Gains | 9,515 | 25,708
Gross Unrealized Losses | (13,714) | 0
Securities available for sale | 1,041,380 | 831,223
Estimated Fair Value, Less Than 12 Months | 1,032,863 | 3,755
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses | (22,142) | (10)
Estimated Fair Value, 12 Months or More | 0 | 0
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses | 0 | 0
Securities Continuous Unrealized Loss Position Fair Value | 1,032,863 | 3,755
SecuritiesContinuousUnrealizedLossPositionAggregateLosses | (22,142) | (10)
US States and Political Subdivisions Debt Securities [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 9,538 | 11,154
Gross Unrealized Gains | 89 | 243
Gross Unrealized Losses | (103) | 0
Securities available for sale | 9,524 | 11,397
Corporate Securities [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 32,088 | 22,941
Gross Unrealized Gains | 973 | 1,444
Gross Unrealized Losses | (112) | 0
Securities available for sale | 32,949 | 24,385
Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage - Backed Securities - Residential [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 632,687 | 481,109
Gross Unrealized Gains | 6,308 | 14,924
Gross Unrealized Losses | (9,021) | 0
Securities available for sale | 629,974 | 496,033
Estimated Fair Value, Less Than 12 Months | 658,965 | 3,755
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses | (14,779) | (10)
Estimated Fair Value, 12 Months or More | 0 | 0
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses | 0 | 0
Securities Continuous Unrealized Loss Position Fair Value | 658,965 | 3,755
SecuritiesContinuousUnrealizedLossPositionAggregateLosses | (14,779) | (10)
Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 1,000 | 100,996
Gross Unrealized Gains | 0 | 2
Gross Unrealized Losses | (19) | 0
Securities available for sale | 981 | 100,998
Estimated Fair Value, Less Than 12 Months | 22,261 |
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses | (644) |
Estimated Fair Value, 12 Months or More | 0 |
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses | 0 |
Securities Continuous Unrealized Loss Position Fair Value | 22,261 |
SecuritiesContinuousUnrealizedLossPositionAggregateLosses | (644) |
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Commercial [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 365,024 | 182,823
Gross Unrealized Gains | 1,725 | 8,357
Gross Unrealized Losses | (4,459) | 0
Securities available for sale | 362,290 | 191,180
Estimated Fair Value, Less Than 12 Months | 320,414 |
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses | (6,398) |
Estimated Fair Value, 12 Months or More | 0 |
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses | 0 |
Securities Continuous Unrealized Loss Position Fair Value | 320,414 |
SecuritiesContinuousUnrealizedLossPositionAggregateLosses | (6,398) |
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Residential [Member] |  |
Investment Securities [Line Items] |  |
Amortized Cost | 5,242 | 6,492
Gross Unrealized Gains | 420 | 738
Gross Unrealized Losses | 0 | 0
Securities available for sale | $ 5,662 | $ 7,230

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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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