Fair Value of Financial Instruments - Assets and Liabilities Carrying at Fair Value on Non-Recurring Basis (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | | | | |
Mar. 31, 2016 | Mar. 31, 2015 | Mar. 31, 2016 | Mar. 31, 2015 | Dec. 31, 2015 | Sep. 30, 2015 | Dec. 31, 2014 | Sep. 30, 2014 |
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items] | | | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value | | $ 73.9 | $ 137.8 | $ 73.9 | $ 137.8 | $ 74.8 | $ 101.3 | | $ 122.5 | $ 117.2 |
Assets | | | | | | | | | | |
Cash and cash equivalents | | 465.6 | 430.3 | 465.6 | 430.3 | | 695.2 | | | 742.8 |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Asset-backed loans | | 136.8 | | 136.8 | | | 226.7 | | | |
Liabilities | | | | | | | | | | |
Debt | | 6,232 | | 6,232 | | | 6,310.5 | [1],[2] | | |
Derivatives, Liabilities | | | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings | | (0.3) | 5.7 | 0.5 | 5.6 | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) | | | | | (0.5) | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases | | 3 | 12 | 8.1 | 22 | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales | | (3.1) | (2.4) | (30) | (6.5) | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements | | (0.5) | | (6) | | | | | | |
Funds Withheld Receivable | | 1,679.4 | | 1,679.4 | | | 1,710.1 | | | |
Corporate Debt Securities [Member] | | | | | | | | | | |
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items] | | | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value | | | 15.8 | | 15.8 | | 14.1 | | 15.8 | 16.3 |
Derivatives, Liabilities | | | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings | | | | (0.5) | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) | | | | | (0.5) | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases | | | | 0 | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales | | | | (13.6) | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements | | | | 0 | | | | | | |
Other Invested Assets [Member] | | | | | | | | | | |
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items] | | | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value | | 0 | | 0 | | | 2.8 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings | | | | 2.7 | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) | | | | 0 | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases | | | | 0 | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales | | | | 0 | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements | | | | (5.5) | | | | | | |
Net transfer In (Out) of Level 3 (a) | | | | 0 | | | | | | |
Level 2 [Member] | | | | | | | | | | |
Liabilities | | | | | | | | | | |
Total debt | [1],[2] | 6,391 | | 6,391 | | | 6,398 | | | |
Level 3 [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Policy loans and other invested assets | [1] | 2.5 | | 2.5 | | | 2.5 | | | |
Asset-backed loans | [1] | 136.8 | | 136.8 | | | 226.7 | | | |
Liabilities | | | | | | | | | | |
Total debt | [1],[2] | 80.7 | | 80.7 | | | 99.1 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Liabilities Related to Investment Contracts, Fair Value Disclosure | [1] | 895.9 | | 895.9 | | | 960.3 | | | |
Recurring [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Liabilities, Fair Value Disclosure, Recurring | | 799.9 | | 799.9 | | | 781.3 | | | |
Funds Withheld Receivable | | 1,679.4 | | 1,679.4 | | | 1,710.1 | | | |
Assets, Fair Value Disclosure, Recurring | | 1,694.6 | | 1,694.6 | | | 1,780.1 | | | |
Recurring [Member] | Foreign Exchange Forward [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | 5.3 | | 5.3 | | | 1.6 | | | |
Recurring [Member] | Commodity Option [Member] | | | | | | | | | | |
Derivatives, Assets | | | | | | | | | | |
Derivatives | | 1.7 | | 1.7 | | | 7.9 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | 2 | | 2 | | | 5.6 | | | |
Recurring [Member] | Interest Rate Contract [Member] | | | | | | | | | | |
Derivatives, Assets | | | | | | | | | | |
Derivatives | | 10.1 | | 10.1 | | | 6.4 | | | |
Recurring [Member] | Interest Rate Swap [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | 2.1 | | 2.1 | | | 2.6 | | | |
Recurring [Member] | Corporate Debt Securities [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Available-for-sale Securities | | 0 | | 0 | | | 14.1 | | | |
Recurring [Member] | Foreign Exchange Contract [Member] | Foreign Exchange Forward [Member] | | | | | | | | | | |
Derivatives, Assets | | | | | | | | | | |
Derivatives | | 3.4 | | 3.4 | | | 6 | | | |
Recurring [Member] | Equity [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Trading Securities | | 0 | | 0 | | | 32.8 | | | |
Recurring [Member] | Other Invested Assets [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Other invested assets | | 0 | | 0 | | | 2.8 | | | |
Recurring [Member] | Level 1 [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Total financial assets | | 0 | | 0 | | | 0 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Financial Liabilities Fair Value Disclosure | | 0 | | 0 | | | 0 | | | |
Liabilities, Fair Value Disclosure, Recurring | | 0 | | 0 | | | 0 | | | |
Funds Withheld Receivable | | 73.9 | | 73.9 | | | 45.8 | | | |
Assets, Fair Value Disclosure, Recurring | | 73.9 | | 73.9 | | | 78.6 | | | |
Recurring [Member] | Level 1 [Member] | FIA embedded derivatives, included in contractholder funds [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | 136.5 | | 136.5 | | | 142.3 | | | |
Recurring [Member] | Level 1 [Member] | Front Street Future Policyholder Benefits Reserve [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | | | | | | 0 | | | |
Recurring [Member] | Level 1 [Member] | Interest Rate Contract [Member] | | | | | | | | | | |
Derivatives, Assets | | | | | | | | | | |
Derivatives | | 0 | | 0 | | | 0 | | | |
Recurring [Member] | Level 1 [Member] | Equity [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Trading Securities | | 0 | | 0 | | | 32.8 | | | |
Recurring [Member] | Level 1 [Member] | Other Invested Assets [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Other invested assets | | 0 | | 0 | | | 0 | | | |
Recurring [Member] | Level 2 [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Total financial assets | | 0 | | 0 | | | 0 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Financial Liabilities Fair Value Disclosure | | 6,391 | | 6,391 | | | 6,398 | | | |
Liabilities, Fair Value Disclosure, Recurring | | 9.4 | | 9.4 | | | 9.8 | | | |
Funds Withheld Receivable | | 1,531.6 | | 1,531.6 | | | 1,579.9 | | | |
Assets, Fair Value Disclosure, Recurring | | 1,546.8 | | 1,546.8 | | | 1,600.2 | | | |
Recurring [Member] | Level 2 [Member] | Foreign Exchange Forward [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | 5.3 | | 5.3 | | | 1.6 | | | |
Recurring [Member] | Level 2 [Member] | Commodity Option [Member] | | | | | | | | | | |
Derivatives, Assets | | | | | | | | | | |
Derivatives | | 1.7 | | 1.7 | | | 7.9 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | 2 | | 2 | | | 5.6 | | | |
Recurring [Member] | Level 2 [Member] | Interest Rate Contract [Member] | | | | | | | | | | |
Derivatives, Assets | | | | | | | | | | |
Derivatives | | 10.1 | | 10.1 | | | 6.4 | | | |
Recurring [Member] | Level 2 [Member] | Interest Rate Swap [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | 2.1 | | 2.1 | | | 2.6 | | | |
Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Available-for-sale Securities | | 0 | | 0 | | | 0 | | | |
Recurring [Member] | Level 2 [Member] | Foreign Exchange Contract [Member] | Foreign Exchange Forward [Member] | | | | | | | | | | |
Derivatives, Assets | | | | | | | | | | |
Derivatives | | 3.4 | | 3.4 | | | 6 | | | |
Recurring [Member] | Level 3 [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Total financial assets | | 139.3 | | 139.3 | | | 229.2 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Financial Liabilities Fair Value Disclosure | | 976.6 | | 976.6 | | | 1,059.4 | | | |
Liabilities, Fair Value Disclosure, Recurring | | 790.5 | | 790.5 | | | 771.5 | | | |
Funds Withheld Receivable | | 73.9 | | 73.9 | | | 84.4 | | | |
Assets, Fair Value Disclosure, Recurring | | 73.9 | | 73.9 | | | 101.3 | | | |
Recurring [Member] | Level 3 [Member] | FIA embedded derivatives, included in contractholder funds [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | 136.5 | | 136.5 | | | 142.3 | | | |
Recurring [Member] | Level 3 [Member] | Interest Rate Contract [Member] | | | | | | | | | | |
Derivatives, Assets | | | | | | | | | | |
Derivatives | | 0 | | 0 | | | 0 | | | |
Recurring [Member] | Level 3 [Member] | Corporate Debt Securities [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Available-for-sale Securities | | 0 | | 0 | | | 14.1 | | | |
Recurring [Member] | Level 3 [Member] | Foreign Exchange Contract [Member] | Foreign Exchange Forward [Member] | | | | | | | | | | |
Derivatives, Assets | | | | | | | | | | |
Derivatives | | | | | | | 0 | | | |
Recurring [Member] | Level 3 [Member] | Other Invested Assets [Member] | Other Invested Assets [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Other invested assets | | 0 | | 0 | | | | | | |
Contingent Purchase Price Reduction Receivable [Member] | | | | | | | | | | |
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items] | | | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value | | | 47 | | 47 | | | | 41.5 | 41.5 |
Derivatives, Liabilities | | | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings | | | 5.5 | | 5.5 | | | | | |
Front Street Future Policyholder Benefits Reserve [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value | | 654 | 584.5 | 654 | 584.5 | 629 | 629.2 | | 496.4 | 151.3 |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings | | 23.9 | 22.4 | 20.2 | 22.6 | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases | | | 73.6 | | 420.5 | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements | | 1.1 | 7.9 | 4.6 | 9.9 | | | | | |
Equity conversion feature of preferred stock [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value | | 790.5 | 740.4 | 790.5 | 740.4 | $ 768.9 | 771.5 | | $ 653.4 | $ 302.1 |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings | | 20.5 | 21.3 | 14.4 | 27.7 | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss) | | 0 | 0 | 0 | 0 | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases | | 0 | 73.6 | 0 | 420.5 | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales | | 0 | 0 | 0 | 0 | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements | | 1.1 | 7.9 | 4.6 | 9.9 | | | | | |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net | | 0 | $ 0 | 0 | $ 0 | | | | | |
Estimate of Fair Value Measurement [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Policy loans and other invested assets | [1] | 2.5 | | 2.5 | | | 2.5 | | | |
Asset-backed loans | [1] | 136.8 | | 136.8 | | | 226.7 | | | |
Liabilities | | | | | | | | | | |
Total debt | [1],[2] | 6,471.7 | | 6,471.7 | | | 6,497.1 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Liabilities Related to Investment Contracts, Fair Value Disclosure | [1] | 895.9 | | 895.9 | | | 960.3 | | | |
Estimate of Fair Value Measurement [Member] | Recurring [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Total financial assets | | 139.3 | | 139.3 | | | 229.2 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Financial Liabilities Fair Value Disclosure | | 7,367.6 | | 7,367.6 | | | 7,457.4 | | | |
Estimate of Fair Value Measurement [Member] | Recurring [Member] | Front Street Future Policyholder Benefits Reserve [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | 654 | | 654 | | | 629.2 | | | |
Reported Value Measurement [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Policy loans and other invested assets | [1] | 2.5 | | 2.5 | | | 2.5 | | | |
Asset-backed loans | [1] | 136.8 | | 136.8 | | | 226.7 | | | |
Total financial assets | | 139.3 | | 139.3 | | | | | | |
Liabilities | | | | | | | | | | |
Total debt | [1],[2] | 6,232 | | 6,232 | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Liabilities Related to Investment Contracts, Fair Value Disclosure | [1] | 1,034.3 | | 1,034.3 | | | 1,084.5 | | | |
Financial Liabilities Fair Value Disclosure | | 7,266.3 | | 7,266.3 | | | | | | |
Reported Value Measurement [Member] | Recurring [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Total financial assets | | | | | | | 229.2 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Financial Liabilities Fair Value Disclosure | | | | | | | 7,395 | | | |
Option Pricing [Member] | Recurring [Member] | Level 3 [Member] | Other Invested Assets [Member] | Other Invested Assets [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Other invested assets | | | | | | | 2.8 | | | |
Discounted Cash Flow [Member] | Recurring [Member] | Level 3 [Member] | | | | | | | | | | |
Fixed maturity securities, available-for-sale: | | | | | | | | | | |
Other invested assets | | 0 | | 0 | | | 2.8 | | | |
Derivatives, Liabilities | | | | | | | | | | |
Funds Withheld Receivable | | 15.1 | | 15.1 | | | 19.5 | | | |
Discounted Cash Flow [Member] | Recurring [Member] | Level 3 [Member] | Front Street Future Policyholder Benefits Reserve [Member] | | | | | | | | | | |
Derivatives, Liabilities | | | | | | | | | | |
Derivative Liability | | $ 654 | | $ 654 | | | $ 629.2 | | | |
| |
[1] | The carrying amounts of cash and cash equivalents, trade receivables, accounts payable and accrued investment income approximate fair value due to their short duration and, accordingly, they are not presented in the tables above. | |
[2] | The fair values of debt set forth above are generally based on quoted or observed market prices. | |