Borrowings (Federal Home Loan Bank Advances Maturity Schedule) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract]
Federal Home Loan Bank advances	$ 593,859	$ 1,141,464
Federal Home Loan Bank of Boston [Member]
Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract]
Scheduled Maturity, Next 12 months	517,222
Scheduled Maturity, Year Two	813
Scheduled Maturity, Year Three	856
Scheduled Maturity, Year Four	35,900
Scheduled Maturity, Year Five	2,751
Scheduled Maturity, Thereafter	36,317
Federal Home Loan Bank advances	$ 593,859	$ 1,100,000
Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate of Amounts Due [Abstract]
Weighted Average Rate, Next 12 months	0.71%
Weighted Average Rate, Year Two	5.12%
Weighted Average Rate, Year Three	5.12%
Weighted Average Rate, Year Four	2.52%
Weighted Average Rate, Year Five	5.03%
Weighted Average Rate, Thereafter	3.13%
Weighted Average Rate, Total	1.00%

Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, Total

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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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Weighted average interest rate of advance from Federal Home Loan Bank (FHLBank) due after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
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Weighted average interest rate of advance from Federal Home Loan Bank (FHLBank) due in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Weighted average interest rate of advance from Federal Home Loan Bank (FHLBank) due in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Weighted average interest rate of advance from Federal Home Loan Bank (FHLBank) due in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Weighted average interest rate of advance from Federal Home Loan Bank (FHLBank) due in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Weighted average interest rate of advance from Federal Home Loan Bank (FHLBank) due in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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