Loans and Leases - Impaired Loans (Details) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
CRE—property development—acquired credit-impaired
Financing Receivable, Impaired [Line Items]
Recorded investment with no related allowance	$ 0	$ 0	$ 0
Unpaid principal balance with no related allowance recorded	34,000,000	34,000,000	34,000,000
CRE—other—acquired credit-impaired
Financing Receivable, Impaired [Line Items]
Recorded investment with no related allowance	0	0	0
Unpaid principal balance with no related allowance recorded	22,000,000	22,000,000	22,000,000
Total CRE
Financing Receivable, Impaired [Line Items]
Recorded investment with no related allowance	0	0	0
Unpaid principal balance with no related allowance recorded	56,000,000	56,000,000	56,000,000
Institutional - commercial and financial lending
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	15,000,000	15,000,000	0
Unpaid principal balance with related allowance recorded	15,000,000	15,000,000	0
Related allowance	2,000,000	2,000,000	0
Average recorded investment of impaired financing receivable	15,000,000	15,000,000
Impaired financing receivable interest revenue	0	0
Total Institutional
Financing Receivable, Impaired [Line Items]
Recorded investment with related allowance	15,000,000	15,000,000	0
Unpaid principal balance with related allowance recorded	15,000,000	15,000,000	0
Related allowance	2,000,000	2,000,000	0
Amount of loan losses related to institutional loans collectively evaluated for impairment	49,000,000	49,000,000	46,000,000
Total CRE and institutional
Financing Receivable, Impaired [Line Items]
Related allowance	2,000,000	2,000,000	0
Total recorded investment	15,000,000	15,000,000	0
Total unpaid principal balance	$ 71,000,000	$ 71,000,000	$ 56,000,000

The balance of financing receivables that were collectively evaluated for impairment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953550-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5258-111524

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