Fair Value Measurements (Narrative) (Detail) $ in Thousands	Jun. 30, 2020 USD ($) security	Dec. 31, 2019 USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Restricted cash	$ 140,400	$ 77,000
Held to maturity debt securities, fair value	460,587	467,966
State And Municipal Obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity debt securities, fair value	445,202	451,353
Corporate Obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity debt securities, fair value	8,450	9,890
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity debt securities, fair value	460,587	467,966
Fair Value | State And Municipal Obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity debt securities, fair value	445,202	451,353
Fair Value | Corporate Obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held to maturity debt securities, fair value	$ 8,450	$ 9,890
Valuation, Market Approach | Measurement Input, Cost to Sell | Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impaired loans, measurement input | security	0.05
Foreclosed assets, measurement input | security	0.05
Valuation, Market Approach | Measurement Input, Cost to Sell | Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impaired loans, measurement input | security	0.10
Foreclosed assets, measurement input | security	0.10