Investments - Allowance for Loan Losses (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2013	Dec. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Collective valuation allowance for losses, beginning of period	$ 1.3	$ 1.3
Addition to/(release of) allowance for losses	0.1	0
Collective valuation allowance for losses, end of period	$ 1.4	$ 1.3

The increase (decrease) in the allowance for credit losses related to financing receivables.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953423-111524

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration