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Investment Securities (Non-agency Commercial Mortgage-backed Securities) (Details) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
Investment securities |  |  |
Fair value investments | $ 4,050.9 | $ 3,343.6 | $ 3,889.0
Fixed rate CMBS |  |  |
Investment securities |  |  |
Average Basis Points of Subordination | 0.25 |  |
Fair value investments | $ 101.1 |  |
Fixed rate CMBS | Super Senior |  |  |
Investment securities |  |  |
Fair value investments | 8.7 |  |
Fixed rate CMBS | Senior |  |  |
Investment securities |  |  |
Fair value investments | 48.6 |  |
Fixed rate CMBS | Subordinate |  |  |
Investment securities |  |  |
Fair value investments | 43.8 |  |
Floating rate CMBS |  |  |
Investment securities |  |  |
Fair value investments | 39.3 |  |
Floating rate CMBS | Super Senior |  |  |
Investment securities |  |  |
Fair value investments | 0.0 |  |
Floating rate CMBS | Senior |  |  |
Investment securities |  |  |
Fair value investments | 0.0 |  |
Floating rate CMBS | Subordinate |  |  |
Investment securities |  |  |
Fair value investments | 39.3 |  |
Commercial |  |  |
Investment securities |  |  |
Fair value investments | 140.4 | $ 109.3 |
Commercial | Super Senior |  |  |
Investment securities |  |  |
Fair value investments | 8.7 |  |
Commercial | Senior |  |  |
Investment securities |  |  |
Fair value investments | 48.6 |  |
Commercial | Subordinate |  |  |
Investment securities |  |  |
Fair value investments | $ 83.1 |  |
Maximum | Commercial |  |  |
Investment securities |  |  |
Loans and Leases Receivable, Ratio of Nonperforming Loans to All Loans | 1.00% |  |

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- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph a, f, g -Article 7 + Details
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