Long-Term Borrowings - Components (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Long-term borrowings
Long-term borrowings	$ 600,028	$ 600,026
Finance lease
Long-term borrowings
Long-term borrowings	$ 28	$ 26
Interest rate (as a percent)	6.78%	6.78%
FHLB short-term advance
Long-term borrowings
Long-term borrowings	$ 600,000	$ 600,000
Remaining borrowing capacity	$ 1,400,000	$ 1,300,000
Interest rate (as a percent)	2.80%	2.80%