Loans Receivable and Allowance for Credit Losses (Composition of Non-PCI and PCI Loans- Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loans receivable pledged to secure borrowings and to provide additional borrowing capacity from the FHLB and the Federal Reserve Bank	$ 18,880,598	$ 16,441,068
Residential \| Minimum
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Adjustable rate mortgage, initial fixed periods	1 year
Residential \| Maximum
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Adjustable rate mortgage, initial fixed periods	7 years
Consumer Lending \| HELOCs
LOANS RECEIVABLE AND ALLOWANCE FOR LOAN LOSSES
Loan to value ratio	60.00%

The term of the initial fixed interest rate period of an adjustable rate mortgage loan.

No definition available.

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- Definition

Ratio which compares the amount of the borrower’s first mortgage with the appraised value of the property. It is computed as Current Loan Balance ÷ Current Appraised Value

+ References

No definition available.

+ Details

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- Definition

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.

+ References

No definition available.

+ Details

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- Definition

Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5086-111524

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