Related Party Transactions - Credit Facilities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Related Party Transaction [Line Items]
Due to affiliate	$ 5.8				$ 8.9
Expense incurred	13.6		30.4
ING Bank N.V.
Related Party Transaction [Line Items]
Due to affiliate	3.2				5.8
Expense incurred	6.6	[1]	18.4	[1]
ING Bank N.V. | Captive Reinsurance Subsidiary
Related Party Transaction [Line Items]
Letters of Credit Outstanding, Amount	15.0
ING Bank N.V. | Senior Unsecured Credit Facility
Related Party Transaction [Line Items]
Due to affiliate	3.1				4.9
Expense incurred	3.7		17.7
Indemnification Agreement [Member] | ING Bank N.V. | NN Group
Related Party Transaction [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 15.0

[1] See "Derivatives" section below.