Basis of Presentation, Significant Accounting Polices and Practicies and Recent Accounting Pronouncements Basis of Presentation - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Millions

3 Months Ended

9 Months Ended

12 Months Ended

Jun. 30, 2017

Jun. 30, 2016

Jun. 30, 2017

Jun. 30, 2016

Sep. 30, 2016

Jan. 13, 2017

Basis of Presentation [Line Items]

Earnings Per Share, Diluted

$ 0.01

$ (0.66)

$ 0.66

$ (0.95)

Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share

0.02

(0.93)

0.82

(1.17)

Income (Loss) from Continuing Operations, Per Diluted Share

(0.01)

0.27

(0.16)

0.22

Earnings Per Share, Basic

0.01

(0.67)

0.66

(0.97)

Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share

0.02

(0.94)

0.82

(1.19)

Income (Loss) from Continuing Operations, Per Basic Share

$ (0.01)

$ 0.27

$ (0.16)

$ 0.22

Net Income (Loss) Attributable to Parent

$ 2.1

$ (132.9)

$ 132.2

$ (191.5)

Less: Net income attributable to noncontrolling interest

37.7

39.9

117.0

121.4

Net income (loss)

39.8

(93.0)

249.2

(70.1)

Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest

7.7

(185.5)

195.4

(222.6)

Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest

32.1

92.5

53.8

152.5

Income tax expense (benefit)

24.8

$ (2.2)

$ 87.4

$ (4.5)

Document Period End Date

Jun. 30, 2017

Deferred Finance Costs, Net

79.8

$ 79.8

$ 87.0

Statutory Accounting Practices, Statutory Capital and Surplus, Increase (Decrease) as a Result of ReDomestication by Entity

$ 28.8

FGL [Member]

Basis of Presentation [Line Items]

Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners

19.60%

Raven Re [Member]

Basis of Presentation [Line Items]

Statutory Accounting Practices, Statutory Capital and Surplus, Balance

$ 115.0

201.3

Statutory Accounting Practices, Permitted Practice, Change in Statutory Capital and Surplus

5.7

4.2

Statutory Accounting Practices, Non-Permitted Practice, Change in Statutory Capital and Surplus

18.7

(4.6)

Statutory Accounting Practices, Statutory Capital and Surplus, Change in Permitted Practice to Non-Permitted, Balance

$ 102.0

102.0

210.0

Net Periodic Benefit Cost [Member]

Basis of Presentation [Line Items]

Defined Benefit Plan, Net Periodic Benefit Cost

7.8

4.8

Defined Benefit Plan, Service Cost

4.3

3.3

Defined Benefit Plan, Other Costs

$ 3.5

$ 1.5

Secured Debt [Member] | Margin Loan, due July 13, 2018 [Member]

Basis of Presentation [Line Items]

Line of Credit Facility, Maximum Borrowing Capacity

$ 150.0