Federal Home Loan Bank Advances and Long-Term Debt (FHLB Advances) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
FHLB advances	$ 326,172	$ 323,891
Available borrowing capacity from FHLB advances	$ 6,110,000	$ 6,830,000
FHLB Advances
Debt Instrument [Line Items]
Weighted-average rate (as a percent)	2.87%	1.85%
FHLB advances that will mature in the next five years
2019	$ 81,900
2020	0
2021	0
2022	$ 244,300
FHLB Advances \| Minimum
Debt Instrument [Line Items]
Variable interest rate	1.79%	0.67%
FHLB Advances \| Maximum
Debt Instrument [Line Items]
Variable interest rate	2.98%	1.95%

Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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Amount of advances or credit lines available from the Federal Home Loan Bank (FHLB).

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