Share-Based Incentive Compensation Plans - Compensation Cost (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 29.1		$ 29.8		$ 87.0		$ 53.2
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	12.3	[1]	6.9	[1]	31.8	[1]	17.9	[1]
RSUs - Deal incentive awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	1.3		7.5		6.9		14.1
Performance shares (PSU awards)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	14.1	[1]	15.4	[1]	45.4	[1]	20.4	[1]
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	0	[2]	0	[2]	0	[2]	0.8	[2]
Phantom Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	1.4		0		2.9
ING Group Share-based Compensation Plans | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	1.8		3.7		5.5		11.7
Long-term Sustainable Performance Plan | Performance shares (PSU awards)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 6.1		$ 9.2		$ 22.8		$ 12.9

[1] These tables include compensation costs of $1.8 and $5.5 for the three and nine months ended September 30, 2014, respectively, related to ING Group RSU awards. In addition, these tables include compensation costs of $3.7 and $11.7 for the three and nine months ended September 30, 2013, respectively, related to ING Group RSU awards.(2) These tables include compensation costs of $6.1 and $22.8 for the three and nine months ended September 30, 2014, respectively, related to ING Group PSU awards. In addition, these tables include compensation costs of $9.2 and $12.9 for the three and nine months ended September 30, 2013, respectively, related to ING Group PSU awards.

[2] ompensation costs recognized during the three and nine months ended September 30, 2013 represents the associated portion with ING Group stock options held by the Company's employees.(4) The Company recognized no income tax benefit due to recognized valuation allowances for periods presented. See the Income Taxes Note to these Condensed Consolidated Financial Statements for additional information.