Borrowings (Trust Preferred Securities) (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2017	Dec. 31, 2016
Trust Preferred Securities [Abstract]
Junior subordinated notes	$ 247	$ 247
Long-term Debt	493	493
6.125% senior notes, matures 2021
Trust Preferred Securities [Abstract]
Senior note	$ 246	$ 246
Interest rate	6.125%	6.125%
3ML plus 3.25% maturing 2032
Trust Preferred Securities [Abstract]
Variable rate on interest rate	3.25%
Junior subordinated notes	$ 26	$ 26
Interest rate	4.55%	4.25%
3ML plus 3.25% maturing 2033 A
Trust Preferred Securities [Abstract]
Variable rate on interest rate	3.25%
Junior subordinated notes	$ 26	$ 26
Interest rate	4.41%	4.13%
3ML plus 3.25% maturing 2033 B
Trust Preferred Securities [Abstract]
Variable rate on interest rate	3.25%
Junior subordinated notes	$ 26	$ 26
Interest rate	4.40%	4.25%
3ML plus 2.00% maturing 2035 A
Trust Preferred Securities [Abstract]
Variable rate on interest rate	2.00%
Junior subordinated notes	$ 26	$ 26
Interest rate	3.16%	2.88%
3ML plus 2.00% maturing 2035 B
Trust Preferred Securities [Abstract]
Variable rate on interest rate	2.00%
Junior subordinated notes	$ 26	$ 26
Interest rate	3.16%	2.88%
3ML plus 1.75% maturing 2035
Trust Preferred Securities [Abstract]
Variable rate on interest rate	1.75%
Junior subordinated notes	$ 51	$ 51
Interest rate	3.00%	2.71%
3ML plus 1.50% maturing 2035
Trust Preferred Securities [Abstract]
Variable rate on interest rate	1.50%
Junior subordinated notes	$ 25	$ 25
Interest rate	2.66%	2.38%
3ML plus 1.45% maturing 2037
Trust Preferred Securities [Abstract]
Variable rate on interest rate	1.45%
Junior subordinated notes	$ 25	$ 25
Interest rate	2.70%	2.41%
3ML plus 2.50% maturing 2037
Trust Preferred Securities [Abstract]
Variable rate on interest rate	2.50%
Junior subordinated notes	$ 16	$ 16
Interest rate	3.75%	3.46%

The trust preferred securities outstanding which are callable by an entity and interest is payable quarterly.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16)(a))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

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