Long-Term Borrowings - Components (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Long-term borrowings
Finance lease liabilities	$ 10	$ 10
Long-term borrowings	$ 200,010	$ 200,010
Finance lease obligation, annual interest rate	6.78%	6.78%
Federal Reserve Bank line of credit
Long-term borrowings
Remaining borrowing capacity	$ 1,200,000	$ 1,100,000
FHLB fixed-rate advances
Long-term borrowings
Long-term borrowings	200,000	200,000
Remaining borrowing capacity	$ 2,000,000	$ 2,000,000
Weighted average interest rate	2.73%	2.73%