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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of transfers of assets measured on a recurring basis out of Level 1 into Level 2 of the fair value hierarchy.

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Amount of transfers of assets measured on a recurring basis out of Level 2 into Level 1 of the fair value hierarchy.

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Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 3.

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Amount of transfers of assets measured on a recurring basis out of Level 3 of the fair value hierarchy into Level 2.

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Fair Value Measurements - Transfers (Details) - Recurring Fair Value Measurements - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Available-for-sale \| Fixed maturities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	$ 15.7	$ 6.7	$ 15.7	$ 26.2
Transfers out of Level 3 into Level 2	32.6	29.7	36.6	91.8
Available-for-sale \| Non-U.S. governments
Fair Value Hierarchy Levels Transfers
Transfers out of Level 3 into Level 2	32.6		32.6
Available-for-sale \| Corporate debt securities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	15.7	6.7	15.7	26.2
Transfers out of Level 3 into Level 2		19.8	1.7	67.5
Available-for-sale \| Commercial mortgage-backed securities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 3 into Level 2			2.3
Available-for-sale \| Other debt obligations
Fair Value Hierarchy Levels Transfers
Transfers out of Level 3 into Level 2		9.9		24.3
Separate account assets
Fair Value Hierarchy Levels Transfers
Transfers out of Level 1 into Level 2	0.2	0.9	26.4	2.0
Transfers out of Level 2 into Level 1	0.2	6.2	4.7	6.8
Transfers out of Level 2 into Level 3	0.1		0.9	0.1
Transfers out of Level 3 into Level 2	$ 0.7	$ 0.1	$ 0.7	0.1
Other investments
Fair Value Hierarchy Levels Transfers
Transfers out of Level 3 into Level 2				$ 35.0