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Shareholders' Equity (Additional Information) (Details) $ / shares in Units, $ in Thousands | 12 Months Ended |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) $ / shares shares | Dec. 31, 2019 USD ($) $ / shares shares | Jan. 31, 2020 shares | Jan. 31, 2019 shares | Dec. 31, 2018 USD ($) | Dec. 31, 2015 USD ($) | Oct. 08, 2015 USD ($) | Sep. 24, 2013 shares
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |  |  |  |  |  |
number of years | 2 |  |  |  |  |  |  |
Dividends declared to shareholders | $ | $ 19,800 | $ 18,900 |  |  | $ 18,000 |  |  |
Subordinated Debt | $ | 59,331 | 59,080 |  |  |  | $ 15,000 | $ 15,000 |
Value Of Trust Preferred Securities Included In Tier 1 Capital | $ | $ 43,000 | 43,000 |  |  |  | 43,000 |  |
Subordinated Debt, Phase-Out Period, Annual, Percentage | 0.20 |  |  |  |  |  |  |
Subsidiaries [Member] |  |  |  |  |  |  |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |  |  |  |  |  |
Dividends declared to shareholders | $ | $ 39,400 | $ 36,900 |  |  | $ 28,100 |  |  |
2013 Common Stock Repurchase Program [Member] |  |  |  |  |  |  |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |  |  |  |  |  |
Stock repurchase program, shares of common stock approved for repurchase |  |  |  |  |  |  |  | 375,000
Stock repurchased during period, shares |  | 750 |  |  |  |  |  |
Shares repurchased, average cost per share | $ / shares |  | $ 26.57 |  |  |  |  |  |
Share Repurchase Program Three [Member] |  |  |  |  |  |  |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |  |  |  |  |  |
Stock repurchase program, shares of common stock approved for repurchase |  |  |  | 775,000 |  |  |  |
Stock repurchased during period, shares | 488,052 |  |  |  |  |  |  |
Shares repurchased, average cost per share | $ / shares | $ 42.61 |  |  |  |  |  |  |
Share Repurchase Program Four [Member] |  |  |  |  |  |  |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |  |  |  |  |  |
Stock repurchase program, shares of common stock approved for repurchase |  |  | 750,000 |  |  |  |  |
Stock repurchased during period, shares | 274,354 |  |  |  |  |  |  |
Shares repurchased, average cost per share | $ / shares |  | $ 35.36 |  |  |  |  |  |
Stock Repurchase Program, Period in Force |  | 12 months |  |  |  |  |  |
Tier II Capital [Member] |  |  |  |  |  |  |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |  |  |  |  |  |  |
Subordinated Debt | $ | $ 12,000 | $ 15,000 |  |  |  | $ 15,000 |  |

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