Condensed Consolidating Financial Information - Statements of Cash Flows (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 3,628.6	$ 3,263.4	$ 3,282.1
Proceeds from the sale, maturity, disposal or redemption of:
Fixed maturities	13,594.0	16,681.3	17,015.2
Equity securities, available-for-sale	70.0	51.6	66.8
Mortgage loans on real estate	1,555.3	1,580.0	1,991.8
Loan - Dutch State obligation	0	0	1,781.9
Limited partnerships/corporations	204.3	466.1	895.9
Acquisition of:
Fixed maturities	(12,985.3)	(19,014.8)	(17,292.3)
Equity securities, available-for-sale	(28.4)	(47.6)	(41.8)
Mortgage loans on real estate	(2,036.4)	(2,206.0)	(1,969.0)
Limited partnerships/corporations	(289.0)	(97.0)	(178.9)
Short-term investments, net	(662.0)	4,943.1	(2,397.4)
Policy loans, net	43.0	53.3	63.6
Derivatives, net	(1,117.4)	(2,623.7)	(1,395.8)
Other investments, net	33.0	53.0	43.4
Sales from consolidated investment entities	3,470.1	3,203.0	1,781.7
Purchases within consolidated investment entities	(5,533.9)	(4,257.9)	(2,851.6)
Maturity of intercompany loans issued with maturities more than three months	0	0
Net maturity of short-term intercompany loans to subsidiaries	0	0	0
Return of capital contributions and dividends from subsidiaries	0	0	0
Capital contributions to subsidiaries	0	0	0
Collateral received (delivered), net	401.5	(629.3)	139.9
Purchases of fixed assets, net	(32.7)	(40.7)	(29.3)
Other, net		0
Net cash used in investing activities	(3,313.9)	(1,885.6)	(2,375.9)
Cash Flows from Financing Activities:
Deposits received for investment contracts	8,153.6	12,893.9	16,118.8
Maturities and withdrawals from investment contracts	(9,899.3)	(14,301.0)	(19,033.4)
Proceeds from issuance of debt with maturities of more than three months	0	2,146.8	3,049.6
Repayment of debt with maturities of more than three months	0	(2,697.4)	(902.5)
Short-term debt	0	(171.6)	(309.1)
Debt issuance costs	(16.8)	(26.5)	(38.8)
Intercompany loans with maturities of more than three months	0	0
Net (repayments of) proceeds from loans to subsidiaries	0	0	0
Return of capital contributions and dividends to parent	0	0	0
Contributions of capital from parent	0	0	0
Borrowings of consolidated investment entities	401.3	196.5	152.6
Repayments of borrowings of consolidated investment entities	(75.8)	(128.2)	(56.6)
Contributions from (distributions to) participants in consolidated investment entities	1,624.9	1,197.3	1,262.0
Proceeds from issuance of common stock	0	571.6	0
Excess tax benefits on share-based compensation	3.9	0	0
Payments Related to Tax Withholding for Share-based Compensation	16.9	0	0
Common stock acquired - Share repurchase	(789.4)	0	0
Dividends paid	(10.1)	(5.2)	0
Net cash (used in) provided by financing activities	(624.6)	(323.8)	242.6
Net increase in cash and cash equivalents	(309.9)	1,054.0	1,148.8
Cash and cash equivalents, beginning of year	2,840.8	1,786.8	638.0
Cash and cash equivalents, end of year	2,530.9	2,840.8	1,786.8
Parent Issuer
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	85.7	203.4	59.7
Proceeds from the sale, maturity, disposal or redemption of:
Fixed maturities	0	0	0
Equity securities, available-for-sale	18.7	14.5	27.2
Mortgage loans on real estate	0	0	0
Loan - Dutch State obligation			0
Limited partnerships/corporations	0	0	0
Acquisition of:
Fixed maturities	0	0	0
Equity securities, available-for-sale	(25.0)	(19.6)	(14.0)
Mortgage loans on real estate	0	0	0
Limited partnerships/corporations	0	0	0
Short-term investments, net	0	0	0
Policy loans, net	0	0	0
Derivatives, net	1.3	(6.6)	0
Other investments, net	0	0	0
Sales from consolidated investment entities	0	0	0
Purchases within consolidated investment entities	0	0	0
Maturity of intercompany loans issued with maturities more than three months	0.9	2.3	0
Net maturity of short-term intercompany loans to subsidiaries	41.5	(136.6)	102.3
Return of capital contributions and dividends from subsidiaries	902.0	1,434.0	813.0
Capital contributions to subsidiaries	(150.0)	(2,062.0)	(400.0)
Collateral received (delivered), net	0	27.7	7.2
Purchases of fixed assets, net	0	0	0
Other, net		0
Net cash used in investing activities	789.4	(746.3)	535.7
Cash Flows from Financing Activities:
Deposits received for investment contracts	0	0	0
Maturities and withdrawals from investment contracts	0	0	0
Proceeds from issuance of debt with maturities of more than three months	0	2,146.8	3,048.5
Repayment of debt with maturities of more than three months	0	(1,370.4)	(902.5)
Short-term debt	0	(171.6)	(309.1)
Debt issuance costs	(16.8)	(26.5)	(38.8)
Intercompany loans with maturities of more than three months	0	0
Net (repayments of) proceeds from loans to subsidiaries	0	(319.1)	(2,037.3)
Return of capital contributions and dividends to parent	0	0	0
Contributions of capital from parent	0	0	0
Borrowings of consolidated investment entities	0	0	0
Repayments of borrowings of consolidated investment entities	0	0	0
Contributions from (distributions to) participants in consolidated investment entities	0	0	0
Proceeds from issuance of common stock	0	571.6	0
Excess tax benefits on share-based compensation	0
Payments Related to Tax Withholding for Share-based Compensation	16.9	0	0
Common stock acquired - Share repurchase	(789.4)	0	0
Dividends paid	(10.1)	(5.2)	0
Net cash (used in) provided by financing activities	(833.2)	825.6	(239.2)
Net increase in cash and cash equivalents	41.9	282.7	356.2
Cash and cash equivalents, beginning of year	640.2	357.5	1.3
Cash and cash equivalents, end of year	682.1	640.2	357.5
Subsidiary Guarantor
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	160.1	83.3	50.5
Proceeds from the sale, maturity, disposal or redemption of:
Fixed maturities	0	0	0
Equity securities, available-for-sale	13.1	14.0	12.0
Mortgage loans on real estate	0	0	0
Loan - Dutch State obligation			0
Limited partnerships/corporations	0	0	0
Acquisition of:
Fixed maturities	0	0	0
Equity securities, available-for-sale	0	(11.1)	(17.5)
Mortgage loans on real estate	0	0.4	0
Limited partnerships/corporations	0	0	0
Short-term investments, net	0	0	0
Policy loans, net	0	0	0
Derivatives, net	0	0	0
Other investments, net	(11.0)	0	1.3
Sales from consolidated investment entities	0	0	0
Purchases within consolidated investment entities	0	0	0
Maturity of intercompany loans issued with maturities more than three months	0	0
Net maturity of short-term intercompany loans to subsidiaries	0	58.0	(33.5)
Return of capital contributions and dividends from subsidiaries	780.0	1,077.0	720.0
Capital contributions to subsidiaries	(171.0)	(0.3)	0
Collateral received (delivered), net	0	0	0
Purchases of fixed assets, net	0	0	0
Other, net		(0.4)
Net cash used in investing activities	611.1	1,137.6	682.3
Cash Flows from Financing Activities:
Deposits received for investment contracts	0	0	0
Maturities and withdrawals from investment contracts	0	0	0
Proceeds from issuance of debt with maturities of more than three months		0	0
Repayment of debt with maturities of more than three months		(638.6)	0
Short-term debt		0	0
Debt issuance costs	0	0	0
Intercompany loans with maturities of more than three months	0	0
Net (repayments of) proceeds from loans to subsidiaries	24.3	125.4	0
Return of capital contributions and dividends to parent	(795.0)	(987.0)	(733.0)
Contributions of capital from parent	0	280.0	0
Borrowings of consolidated investment entities	0	0	0
Repayments of borrowings of consolidated investment entities	0	0	0
Contributions from (distributions to) participants in consolidated investment entities	0	0	0
Proceeds from issuance of common stock		0
Excess tax benefits on share-based compensation	0
Payments Related to Tax Withholding for Share-based Compensation	0
Common stock acquired - Share repurchase	0
Dividends paid	0	0
Net cash (used in) provided by financing activities	(770.7)	(1,220.2)	(733.0)
Net increase in cash and cash equivalents	0.5	0.7	(0.2)
Cash and cash equivalents, beginning of year	1.1	0.4	0.6
Cash and cash equivalents, end of year	1.6	1.1	0.4
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	3,565.8	3,076.7	3,264.9
Proceeds from the sale, maturity, disposal or redemption of:
Fixed maturities	13,594.0	16,681.3	17,015.2
Equity securities, available-for-sale	38.2	23.1	27.6
Mortgage loans on real estate	1,555.3	1,580.0	1,991.8
Loan - Dutch State obligation			1,781.9
Limited partnerships/corporations	204.3	466.1	895.9
Acquisition of:
Fixed maturities	(12,985.3)	(19,014.8)	(17,292.3)
Equity securities, available-for-sale	(3.4)	(16.9)	(10.3)
Mortgage loans on real estate	(2,036.4)	(2,206.4)	(1,969.0)
Limited partnerships/corporations	(289.0)	(97.0)	(178.9)
Short-term investments, net	(662.0)	4,943.1	(2,397.4)
Policy loans, net	43.0	53.3	63.6
Derivatives, net	(1,118.7)	(2,617.1)	(1,395.8)
Other investments, net	44.0	53.0	42.1
Sales from consolidated investment entities	3,470.1	3,203.0	1,781.7
Purchases within consolidated investment entities	(5,533.9)	(4,257.9)	(2,851.6)
Maturity of intercompany loans issued with maturities more than three months	0	0
Net maturity of short-term intercompany loans to subsidiaries	0	261.1	2,070.8
Return of capital contributions and dividends from subsidiaries	0	0	0
Capital contributions to subsidiaries	0	0	0
Collateral received (delivered), net	401.5	(657.0)	132.7
Purchases of fixed assets, net	(32.7)	(40.7)	(29.3)
Other, net		0.4
Net cash used in investing activities	(3,311.0)	(1,643.4)	(321.3)
Cash Flows from Financing Activities:
Deposits received for investment contracts	8,153.6	12,893.9	16,118.8
Maturities and withdrawals from investment contracts	(9,899.3)	(14,301.0)	(19,033.4)
Proceeds from issuance of debt with maturities of more than three months		0	1.1
Repayment of debt with maturities of more than three months		(688.4)	0
Short-term debt		0	0
Debt issuance costs	0	0	0
Intercompany loans with maturities of more than three months	(0.9)	(2.3)
Net (repayments of) proceeds from loans to subsidiaries	(65.8)	11.2	(102.3)
Return of capital contributions and dividends to parent	(1,070.0)	(1,624.0)	(893.0)
Contributions of capital from parent	321.0	1,782.3	400.0
Borrowings of consolidated investment entities	401.3	196.5	152.6
Repayments of borrowings of consolidated investment entities	(75.8)	(128.2)	(56.6)
Contributions from (distributions to) participants in consolidated investment entities	1,624.9	1,197.3	1,262.0
Proceeds from issuance of common stock		0
Excess tax benefits on share-based compensation	3.9
Payments Related to Tax Withholding for Share-based Compensation	0
Common stock acquired - Share repurchase	0
Dividends paid	0	0
Net cash (used in) provided by financing activities	(607.1)	(662.7)	(2,150.8)
Net increase in cash and cash equivalents	(352.3)	770.6	792.8
Cash and cash equivalents, beginning of year	2,199.5	1,428.9	636.1
Cash and cash equivalents, end of year	1,847.2	2,199.5	1,428.9
Consolidating Adjustments
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(183.0)	(100.0)	(93.0)
Proceeds from the sale, maturity, disposal or redemption of:
Fixed maturities	0	0	0
Equity securities, available-for-sale	0	0	0
Mortgage loans on real estate	0	0	0
Loan - Dutch State obligation			0
Limited partnerships/corporations	0	0	0
Acquisition of:
Fixed maturities	0	0	0
Equity securities, available-for-sale	0	0	0
Mortgage loans on real estate	0	0	0
Limited partnerships/corporations	0	0	0
Short-term investments, net	0	0	0
Policy loans, net	0	0	0
Derivatives, net	0	0	0
Other investments, net	0	0	0
Sales from consolidated investment entities	0	0	0
Purchases within consolidated investment entities	0	0	0
Maturity of intercompany loans issued with maturities more than three months	(0.9)	(2.3)
Net maturity of short-term intercompany loans to subsidiaries	(41.5)	(182.5)	(2,139.6)
Return of capital contributions and dividends from subsidiaries	(1,682.0)	(2,511.0)	(1,533.0)
Capital contributions to subsidiaries	321.0	2,062.3	400.0
Collateral received (delivered), net	0	0	0
Purchases of fixed assets, net	0	0	0
Other, net		0
Net cash used in investing activities	(1,403.4)	(633.5)	(3,272.6)
Cash Flows from Financing Activities:
Deposits received for investment contracts	0	0	0
Maturities and withdrawals from investment contracts	0	0	0
Proceeds from issuance of debt with maturities of more than three months		0	0
Repayment of debt with maturities of more than three months		0	0
Short-term debt		0	0
Debt issuance costs	0	0	0
Intercompany loans with maturities of more than three months	0.9	2.3
Net (repayments of) proceeds from loans to subsidiaries	41.5	182.5	2,139.6
Return of capital contributions and dividends to parent	1,865.0	2,611.0	1,626.0
Contributions of capital from parent	(321.0)	(2,062.3)	(400.0)
Borrowings of consolidated investment entities	0	0	0
Repayments of borrowings of consolidated investment entities	0	0	0
Contributions from (distributions to) participants in consolidated investment entities	0	0	0
Proceeds from issuance of common stock		0
Excess tax benefits on share-based compensation	0
Payments Related to Tax Withholding for Share-based Compensation	0
Common stock acquired - Share repurchase	0
Dividends paid	0	0
Net cash (used in) provided by financing activities	1,586.4	733.5	3,365.6
Net increase in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	$ 0	$ 0	$ 0