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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