Income Taxes - Unrecognized Tax Benefits and Deferred Income Taxes (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended			12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Changes in Unrecognized Tax Benefits
Beginning balance, Unrecognized tax benefits			$ 172.4			$ 172.4	$ 108.9
Additions based on tax positions related to the current year						12.9	12.9
Additions for tax positions of prior years						45.9	62.5
Reductions for tax positions related to the current year						(8.7)	(8.4)
Reductions for tax positions of prior years						(3.5)	(0.2)
Settlements							(3.3)
Ending balance, Unrecognized tax benefits						219.0	172.4	$ 108.9
Amount of unrecognized tax benefits that would reduce the effective income tax rate, if recognized						79.5
Accumulated pre-tax interest and penalties related to unrecognized tax benefits						137.9	100.4
Net deferred income taxes by jurisdiction
Net deferred income tax assets						96.0	90.8
Deferred income taxes						(697.2)	(1,035.3)
Total net deferred income tax liabilities						(601.2)	(944.5)
Current income taxes (benefits):
U.S. federal						225.9	242.1	109.5
Total current income taxes (benefits)						218.8	151.4	52.8
Deferred income taxes (benefits)						$ (41.2)	$ 167.1	$ 135.1
Reconciliation between the U.S. corporate income tax rate and the effective income tax rate from continuing operations
U.S. corporate statutory income tax rate (as a percent)						35.00%	35.00%	35.00%
Dividends received deduction (as a percent)						(11.00%)	(10.00%)	(10.00%)
Merger of Chilean legal entities (as a percent)						(7.00%)
Impact of equity method presentation (as a percent)						(3.00%)	(2.00%)	(3.00%)
Tax credits (as a percent)						(2.00%)	(2.00%)
Interest exclusion from taxable income (as a percent)						(1.00%)	(1.00%)	(2.00%)
Foreign tax rate differential (as a percent)							(2.00%)	(2.00%)
Impact of court ruling on some uncertain tax positions (as a percent)						3.00%
Impact of enactment of tax legislation (as a percent)							4.00%	1.00%
Other income tax rate impacts (as a percent)						(2.00%)	(1.00%)	(2.00%)
Effective income tax rate (as a percent)						12.00%	21.00%	17.00%
Deferred income tax assets:
Insurance liabilities						$ 85.8	$ 390.8
Investments, including derivative liabilities						368.8	395.1
Net operating loss carryforwards						80.9	128.4
Tax credit carryforwards						227.4	163.2
Employee benefits						534.8	506.6
Foreign currency translation						123.4	61.8
Other deferred income tax assets						64.3	94.5
Gross deferred income tax assets						1,485.4	1,740.4
Valuation allowance						(11.9)	(4.1)
Total deferred income tax assets						1,473.5	1,736.3
Deferred income tax liabilities:
Deferred income tax liabilities: Deferred acquisition costs						(866.1)	(774.2)
Investments, including derivative assets						(379.6)	(411.1)
Net unrealized gains on available-for-sale securities						(431.2)	(1,004.6)
Deferred income tax liabilities: Real estate						(123.1)	(133.9)
Intangible assets						(235.4)	(314.2)
Other deferred income tax liabilities						(39.3)	(42.8)
Total deferred income tax liabilities						(2,074.7)	(2,680.8)
Total net deferred income tax liabilities						(601.2)	(944.5)
Deferred income tax disclosures
Accumulated but undistributed earnings from operations of foreign subsidiaries for which U.S. federal and state deferred income taxes have not been provided						1,004.6	824.8
Excess book carrying value over tax basis with respect to the original investment of foreign subsidiaries for which U.S. federal and state deferred income taxes have not been provided						106.2
Impact of court ruling on uncertain tax positions			$ (30.3)		$ (47.5)
Current income tax receivables associated with outstanding audit issues
Current income tax (receivables) payables associated with outstanding audit issues						(229.9)	(298.3)
Brazil
Deferred income tax liabilities:
Transition period for tax increases per enacted tax legislation	3 years
Chile
Deferred income tax liabilities:
Transition period for tax increases per enacted tax legislation		5 years
Deferred income tax disclosures
Increase in net deferred tax liabilities resulting from enactment of tax legislation				$ 58.1
U.S. Federal
Net deferred income taxes by jurisdiction
Deferred income taxes						(459.5)	(663.7)
Deferred income tax assets:
Tax credit carryforwards						227.4	163.2
State
Net deferred income taxes by jurisdiction
Net deferred income tax assets						53.3	35.3
Deferred income tax disclosures-operating loss carryforwards
Net operating loss carryforwards						387.7	408.7
Foreign
Net deferred income taxes by jurisdiction
Net deferred income tax assets						42.7	55.5
Deferred income taxes						(237.7)	(371.6)
Deferred income tax disclosures-operating loss carryforwards
Net operating loss carryforwards						197.1	231.9
Deferred income tax disclosures
Valuation allowances on income tax benefits primarily associated with foreign net operating loss carryforwards						$ 11.9	$ 4.1