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Debt - Summary of Interest Paid (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2017 | Mar. 31, 2016
Debt Instrument [Line Items] |  |
Total interest payments | $ 13.6 | $ 6.3
FHLB Advance |  |
Debt Instrument [Line Items] |  |
Total interest payments | 0.7 | 0.2
Convertible Senior Notes |  |
Debt Instrument [Line Items] |  |
Total interest payments | $ 0.0 | 1.8
Stated interest rate (in hundredths) | 5.00% |
5.75% Notes | 5.75% Notes |  |
Debt Instrument [Line Items] |  |
Total interest payments | $ 12.9 | 0.0
Stated interest rate (in hundredths) | 5.75% |
9% Debentures |  |
Debt Instrument [Line Items] |  |
Total interest payments | $ 0.0 | $ 4.3
Stated interest rate (in hundredths) | 9.00% |

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The amount of cash paid for interest during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3536-108585 + Details
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