Investment Securities (Narrative) (Details) - USD ($)	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Schedule of Held-to-maturity Securities [Line Items]
OTTI recognized in earnings or other comprehensive income	$ 0	$ 0
Deposits [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities pledged as collateral	900,000,000
Federal Reserve Bank Advances [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities pledged as collateral	2,500,000,000
Federal Home Loan Bank of San Francisco [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities pledged as collateral	$ 21,900,000,000

The carrying amount of held-to-maturity securities that serve as collateral for borrowings.

Reference 1: 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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- Definition

The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 8B
-URI http://asc.fasb.org/extlink&oid=82897076&loc=SL6284393-111563

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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.

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