Allowance for Credit Losses on Off-Balance Sheet Credit Exposures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for credit losses for off-balance sheet credit exposure			$ 0
Provision for credit losses	$ 14,717	$ 200
Retained earnings	$ 686,397			$ 695,273
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, Effect On Off-Balance Sheet Items
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings			$ 2,400