Derivatives and Hedging Activities - Impact of Fair Value Hedge Accounting on the Carrying Value of the Hedged Items (Details) $ in Thousands	Sep. 30, 2019 USD ($)
Derivatives, Fair Value [Line Items]
Carrying value of hedged items	$ 1,612,208
Cumulative gain (loss) fair value hedge adjustment included in carrying amount of hedged items	(2,680)
Loans receivable
Derivatives, Fair Value [Line Items]
Carrying value of hedged items	1,612,208
Cumulative gain (loss) fair value hedge adjustment included in carrying amount of hedged items	(2,680)
Mortgage loan fair value hedges
Derivatives, Fair Value [Line Items]
Cumulative gain (loss) fair value hedge adjustment included in carrying amount of hedged items	1,608
Amortized cost basis of the hedged loans	200,000
Mortgage loan fair value hedges \| Loans receivable
Derivatives, Fair Value [Line Items]
Carrying value of hedged items	1,520,647
Commercial loan fair value hedges
Derivatives, Fair Value [Line Items]
Cumulative gain (loss) fair value hedge adjustment included in carrying amount of hedged items	(4,288)
Commercial loan fair value hedges \| Loans receivable
Derivatives, Fair Value [Line Items]
Carrying value of hedged items	$ 91,561

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109999712-113959

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- Definition

Amount of asset hedged in last of layer, expected to be remaining at end of hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EEE
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109999718-113959

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- Definition

Amount of liability hedged in fair value hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109999712-113959

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