Related Party Transactions - Income Statement Disclosures (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Related Party Transaction [Line Items]
Income	$ 11.0		$ 7.8
Expense incurred	13.6		30.4
NN Group
Related Party Transaction [Line Items]
Income	0.6	[1]	0.4	[1]
Expense incurred	0.1	[1]	3.3	[1]
ING Group
Related Party Transaction [Line Items]
Income	5.6		4.2
Expense incurred	3.5		5.0
ING Bank N.V.
Related Party Transaction [Line Items]
Income	(0.5)	[1]	(0.4)	[1]
Expense incurred	6.6	[1]	18.4	[1]
Other
Related Party Transaction [Line Items]
Income	5.3		3.6
Expense incurred	$ 3.4		$ 3.7

[1] See "Derivatives" section below.