Allowance for Credit Losses on Off-Balance Sheet Credit Exposures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Jan. 01, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for credit losses for off-balance sheet credit exposure	$ 4,100		$ 5,000	$ 0
Retained earnings	748,574		$ 718,090
Provision (benefit) charge for credit losses	(15,001)	$ 14,717
Credit loss (benefit) expense for off-balance sheet credit exposures	$ 875	$ (1,000)
Cumulative Effect, Period of Adoption, Adjusted Balance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for credit losses for off-balance sheet credit exposure				3,206
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for credit losses for off-balance sheet credit exposure				3,206
Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for credit losses for off-balance sheet credit exposure				3,200
Accounting Standards Update 2016-13, Effect On Off-Balance Sheet Items
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings				$ 2,400