Fair Value Measurements (Financial Instruments) (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Financial assets:
Cash and cash equivalents	$ 158,282	$ 180,185	$ 233,783	$ 186,438
Available for sale debt securities, at fair value	1,666,306	1,690,112
Investment securities held to maturity, fair value	341,459	352,601
Federal Home Loan Bank stock	77,750	79,217
Equity securities	1,341	1,270
Total loans	10,736,278	10,766,501
Derivative assets	117,452	105,164
Financial liabilities:
Certificates of deposit	1,031,980	1,095,942
Total deposits	10,098,892	10,292,514
Borrowed funds	2,058,098	1,970,033
Subordinated debentures	10,744	10,695
Derivative liabilities	103,314	90,834
Quoted Prices in Active  Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	158,352	180,255
Available for sale debt securities, at fair value	252,387	253,878
Investment securities held to maturity, fair value	16,192	15,553
Federal Home Loan Bank stock	77,750	79,217
Equity securities	1,341	1,270
Total loans	0	0
Derivative assets	0	0
Financial liabilities:
Deposits other than certificates of deposits	9,066,912	9,196,572
Certificates of deposit	0	0
Total deposits	9,066,912	9,196,572
Borrowed funds	0	0
Subordinated debentures	0	0
Derivative liabilities	0	0
Significant Other Observable Inputs (Level 2)
Financial assets:
Cash and cash equivalents	0	0
Available for sale debt securities, at fair value	1,413,919	1,436,234
Investment securities held to maturity, fair value	325,267	337,048
Federal Home Loan Bank stock	0	0
Equity securities	0	0
Total loans	0	0
Derivative assets	114,427	101,754
Financial liabilities:
Deposits other than certificates of deposits	0	0
Certificates of deposit	1,029,290	1,093,125
Total deposits	1,029,290	1,093,125
Borrowed funds	2,043,545	1,960,174
Subordinated debentures	9,504	9,198
Derivative liabilities	101,256	88,835
Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	0	0
Available for sale debt securities, at fair value	0	0
Investment securities held to maturity, fair value	0	0
Federal Home Loan Bank stock	0	0
Equity securities	0	0
Total loans	10,343,089	10,437,204
Derivative assets	0	0
Financial liabilities:
Deposits other than certificates of deposits	0	0
Certificates of deposit	0	0
Total deposits	0	0
Borrowed funds	0	0
Subordinated debentures	0	0
Derivative liabilities	0	0
U.S. Treasury obligations
Financial assets:
Available for sale debt securities, at fair value	252,387	253,878
Investment securities held to maturity, fair value	5,767	5,147
U.S. Treasury obligations | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Financial assets:
Available for sale debt securities, at fair value	252,387	253,878
Investment securities held to maturity, fair value	5,767	5,147
U.S. Treasury obligations | Significant Other Observable Inputs (Level 2)
Financial assets:
Available for sale debt securities, at fair value	0	0
Investment securities held to maturity, fair value	0	0
U.S. Treasury obligations | Significant Unobservable Inputs (Level 3)
Financial assets:
Available for sale debt securities, at fair value	0	0
Investment securities held to maturity, fair value	0	0
Agency-guaranteed obligations
Financial assets:
Available for sale debt securities, at fair value	23,518	27,498
Investment securities held to maturity, fair value	10,425	10,406
Agency-guaranteed obligations | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Financial assets:
Available for sale debt securities, at fair value	0	0
Investment securities held to maturity, fair value	10,425	10,406
Agency-guaranteed obligations | Significant Other Observable Inputs (Level 2)
Financial assets:
Available for sale debt securities, at fair value	23,518	27,498
Investment securities held to maturity, fair value	0	0
Agency-guaranteed obligations | Significant Unobservable Inputs (Level 3)
Financial assets:
Available for sale debt securities, at fair value	0	0
Investment securities held to maturity, fair value	0	0
Mortgage-backed securities
Financial assets:
Available for sale debt securities, at fair value	1,259,881	1,285,609
Mortgage-backed securities | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Financial assets:
Available for sale debt securities, at fair value	0	0
Mortgage-backed securities | Significant Other Observable Inputs (Level 2)
Financial assets:
Available for sale debt securities, at fair value	1,259,881	1,285,609
Mortgage-backed securities | Significant Unobservable Inputs (Level 3)
Financial assets:
Available for sale debt securities, at fair value	0	0
Asset-backed securities
Financial assets:
Available for sale debt securities, at fair value	30,517	32,235
Asset-backed securities | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Financial assets:
Available for sale debt securities, at fair value	0	0
Asset-backed securities | Significant Other Observable Inputs (Level 2)
Financial assets:
Available for sale debt securities, at fair value	30,517	32,235
Asset-backed securities | Significant Unobservable Inputs (Level 3)
Financial assets:
Available for sale debt securities, at fair value	0	0
State and municipal obligations
Financial assets:
Available for sale debt securities, at fair value	55,765	56,584
Investment securities held to maturity, fair value	319,070	330,360
State and municipal obligations | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Financial assets:
Available for sale debt securities, at fair value	0	0
Investment securities held to maturity, fair value	0	0
State and municipal obligations | Significant Other Observable Inputs (Level 2)
Financial assets:
Available for sale debt securities, at fair value	55,765	56,584
Investment securities held to maturity, fair value	319,070	330,360
State and municipal obligations | Significant Unobservable Inputs (Level 3)
Financial assets:
Available for sale debt securities, at fair value	0	0
Investment securities held to maturity, fair value	0	0
Corporate obligations
Financial assets:
Available for sale debt securities, at fair value	44,238	34,308
Investment securities held to maturity, fair value	6,197	6,688
Corporate obligations | Quoted Prices in Active  Markets for Identical Assets (Level 1)
Financial assets:
Available for sale debt securities, at fair value	0	0
Investment securities held to maturity, fair value	0	0
Corporate obligations | Significant Other Observable Inputs (Level 2)
Financial assets:
Available for sale debt securities, at fair value	44,238	34,308
Investment securities held to maturity, fair value	6,197	6,688
Corporate obligations | Significant Unobservable Inputs (Level 3)
Financial assets:
Available for sale debt securities, at fair value	0	0
Investment securities held to maturity, fair value	0	0
Carrying value
Financial assets:
Cash and cash equivalents	158,352	180,255
Available for sale debt securities, at fair value	1,666,306	1,690,112
Investment securities held to maturity, fair value	354,671	363,080
Federal Home Loan Bank stock	77,750	79,217
Equity securities	1,341	1,270
Total loans	10,736,278	10,766,501
Derivative assets	114,427	101,754
Financial liabilities:
Deposits other than certificates of deposits	9,066,912	9,196,572
Certificates of deposit	1,031,980	1,095,942
Total deposits	10,098,892	10,292,514
Borrowed funds	2,058,098	1,970,033
Subordinated debentures	10,744	10,695
Derivative liabilities	101,256	88,835
Carrying value | U.S. Treasury obligations
Financial assets:
Available for sale debt securities, at fair value	252,387	253,878
Investment securities held to maturity, fair value	5,767	5,146
Carrying value | Agency-guaranteed obligations
Financial assets:
Available for sale debt securities, at fair value	23,518	27,498
Investment securities held to maturity, fair value	11,058	11,058
Carrying value | Mortgage-backed securities
Financial assets:
Available for sale debt securities, at fair value	1,259,881	1,285,609
Carrying value | Asset-backed securities
Financial assets:
Available for sale debt securities, at fair value	30,517	32,235
Carrying value | State and municipal obligations
Financial assets:
Available for sale debt securities, at fair value	55,765	56,584
Investment securities held to maturity, fair value	331,278	339,789
Carrying value | Corporate obligations
Financial assets:
Available for sale debt securities, at fair value	44,238	34,308
Investment securities held to maturity, fair value	6,568	7,087
Fair value
Financial assets:
Cash and cash equivalents	158,352	180,255
Available for sale debt securities, at fair value	1,666,306	1,690,112
Investment securities held to maturity, fair value	341,459	352,601
Federal Home Loan Bank stock	77,750	79,217
Equity securities	1,341	1,270
Total loans	10,343,089	10,437,204
Derivative assets	114,427	101,754
Financial liabilities:
Deposits other than certificates of deposits	9,066,912	9,196,572
Certificates of deposit	1,029,290	1,093,125
Total deposits	10,096,202	10,289,697
Borrowed funds	2,043,545	1,960,174
Subordinated debentures	9,504	9,198
Derivative liabilities	101,256	88,835
Fair value | U.S. Treasury obligations
Financial assets:
Available for sale debt securities, at fair value	252,387	253,878
Investment securities held to maturity, fair value	5,767	5,147
Fair value | Agency-guaranteed obligations
Financial assets:
Available for sale debt securities, at fair value	23,518	27,498
Investment securities held to maturity, fair value	10,425	10,406
Fair value | Mortgage-backed securities
Financial assets:
Available for sale debt securities, at fair value	1,259,881	1,285,609
Fair value | Asset-backed securities
Financial assets:
Available for sale debt securities, at fair value	30,517	32,235
Fair value | State and municipal obligations
Financial assets:
Available for sale debt securities, at fair value	55,765	56,584
Investment securities held to maturity, fair value	319,070	330,360
Fair value | Corporate obligations
Financial assets:
Available for sale debt securities, at fair value	44,238	34,308
Investment securities held to maturity, fair value	$ 6,197	$ 6,688