Acquisitions - VOBA and Other Intangible Assets Maturities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Present Value of Future Insurance Profits, Amortization Expense, Next Five Years [Abstract]
Total	$ 2,554.7	$ 3,157.8
TWG Holdings Limited
Present Value of Future Insurance Profits, Amortization Expense, Next Five Years [Abstract]
July 1 - December 31, 2019	503.9
2020	812.7
2021	570.6
2022	350.8
2023	203.7
2024	91.7
Thereafter	7.5
Total	2,540.9
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
July 1 - December 31, 2019	9.5
2020	26.1
2021	31.0
2022	34.9
2023	36.2
2024	36.6
Thereafter	254.1
Total	$ 428.4

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Finite-Lived Intangible Assets, Amortization Expense, Year Six

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Present Value of Future Insurance Profits, Amortization Expense, Year Six

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized in the remainder of the fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of amortization expense expected to be recognized in remainder of fiscal year following latest fiscal year ended for present value of future profits of insurance contract acquired in business combination.

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Amount of amortization expense expected to be recognized during fifth fiscal year following latest fiscal year for present value of future profits of insurance contract acquired in business combination.

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Amount of amortization expense expected to be recognized during fourth fiscal year following latest fiscal year for present value of future profits of insurance contract acquired in business combination.

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Amount of amortization expense expected to be recognized during second fiscal year following latest fiscal year for present value of future profits of insurance contract acquired in business combination.

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