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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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- Definition

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

+ References

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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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Available-for-sale \| Fixed maturities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	$ 123.3	$ 15.7	$ 128.6	$ 15.7
Transfers out of Level 3 into Level 2	62.6	32.6	156.8	36.6
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	17.6	15.7	22.2	15.7
Transfers out of Level 3 into Level 2	37.3		37.3	1.7
Available-for-sale \| Commercial mortgage-backed securities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	17.3		18.0
Transfers out of Level 3 into Level 2	21.7		31.2	2.3
Available-for-sale \| Collateralized debt obligations
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	88.3		88.3
Available-for-sale \| Other debt obligations
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3	0.1		0.1
Transfers out of Level 3 into Level 2	3.6		88.3
Trading \| Fixed maturities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3			1.9
Trading \| Equity securities
Fair Value Hierarchy Levels Transfers
Transfers out of Level 2 into Level 3			0.7
Separate account assets
Fair Value Hierarchy Levels Transfers
Transfers out of Level 1 into Level 2	5.7	0.2	6.4	26.4
Transfers out of Level 2 into Level 1	0.2	0.2	0.2	4.7
Transfers out of Level 2 into Level 3	2.1	0.1	2.1	0.9
Transfers out of Level 3 into Level 2	$ 21.5	$ 0.7	$ 22.4	$ 0.7