Accumulated Other Comprehensive Income - Changes in AOCI, including Reclassification Adjustments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Available-for-sale securities, Before-Tax Amount:
Net unrealized gains/losses on Other	$ (0.3)		$ 11.6
Other-than-temporary impairments	15.6		10.9
Adjustments for amounts recognized in Net realized capital gains (losses) in the Condensed Consolidated Statements of Operations	(8.8)		(14.6)
DAC/VOBA	(459.7)	[1]	386.0	[1]
Sales inducements	(16.7)		28.4
Net realized gains/losses on available-for-sale securities	1,102.5		(376.1)
Available-for-sale securities, Income Tax:
Net unrealized gains/losses on Other	0.1		(4.1)
Change in OTTI, Income Tax	(5.5)		(3.8)
Adjustments for amounts recognized in Net realized capital gains (losses) in the Condensed Consolidated Statements of Operations	3.1		5.1
DAC/VOBA	160.9		(135.1)
Sales inducements	5.8		(9.9)
Net realized gains/losses on available-for-sale securities	(387.0)		128.8
Available-for-sale securities, After-Tax Amount:
Net unrealized gains/losses on Other	(0.2)		7.5
Change in OTTI, After-Tax Amount	10.1		7.1
Adjustments for amounts recognized in Net realized capital gains (losses) in the Condensed Consolidated Statements of Operations	(5.7)		(9.5)
DAC/VOBA	(298.8)		250.9
Sales inducements	(10.9)		18.5
Net realized gains/losses on available-for-sale securities	715.5		(247.3)
Derivatives, Before-Tax Amount:
Net unrealized capital gains/losses arising during the period, Before-Tax Amount	24.6	[2]	(12.7)	[2]
Adjustments for amounts recognized in Net investment income in the Condensed Consolidated Statements of Operations	(1.4)		(0.2)
Net unrealized gains/losses on derivatives	23.2		(12.9)
Derivatives, Income Tax:
Net unrealized capital gains/losses arising during the period, Income Tax	(8.6)		4.5
Adjustments for amounts recognized in Net investment income in the Condensed Consolidated Statements of Operations	0.5		0.1
Net unrealized gains/losses on derivatives	(8.1)		4.6
Derivatives, After-Tax Amount:
Net unrealized capital gains/losses arising during the period, After-Tax Amount	16.0		(8.2)
Adjustments for amounts recognized in Net investment income in the Condensed Consolidated Statements of Operations	(0.9)		(0.1)
Net unrealized gains/losses on derivatives	15.1		(8.3)
Pension and other post-employment benefit liability, Before-Tax Amount:
Amortization of prior service cost recognized in Operating expenses in the Condensed Consolidated Statements of Operations	(3.4)		(3.5)
Net pension and other post-employment benefit liability	(3.4)		(3.5)
Other comprehensive income (loss), before tax	1,122.3		(392.5)
Pension and other post-employment benefit liability, Income Tax:
Amortization of prior service cost recognized in Operating expenses in the Condensed Consolidated Statements of Operations	1.2		1.2
Net pension and other post-employment benefit liability	1.2		1.2
Other comprehensive income (loss)	(393.9)		134.6
Pension and other post-employment benefit liability, After-Tax Amount:
Amortization of prior service cost recognized in Operating expenses in the Condensed Consolidated Statements of Operations	(2.2)		(2.3)
Net pension and other post-employment benefit liability	(2.2)		(2.3)
Other comprehensive income (loss), after tax	728.4		(257.9)
Fixed maturities
Available-for-sale securities, Before-Tax Amount:
Net unrealized gains/losses on securities	1,588.4		(792.1)
Available-for-sale securities, Income Tax:
Net unrealized gains/losses on securities	(555.6)		274.4
Available-for-sale securities, After-Tax Amount:
Net unrealized gains/losses on securities	1,032.8		(517.7)
Equity securities
Available-for-sale securities, Before-Tax Amount:
Net unrealized gains/losses on securities	(16.0)		(6.3)
Available-for-sale securities, Income Tax:
Net unrealized gains/losses on securities	4.2		2.2
Available-for-sale securities, After-Tax Amount:
Net unrealized gains/losses on securities	$ (11.8)		$ (4.1)

[1] See Note 5. Deferred Policy Acquisition Costs and Value of Business Acquired to these Condensed Consolidated Financial Statements for additional information.

[2] See Note 3. Derivative Financial Instruments to these Condensed Consolidated Financial Statements for additional information.