Loans Receivable and Other Lending Investments, net (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Receivables [Abstract]
Carrying value of loans sold	$ 30.8star_LoansSoldLoansCarryingValue	$ 95.1star_LoansSoldLoansCarryingValue	$ 53.9star_LoansSoldLoansCarryingValue
Realized investment gains (losses)	$ 19.1us-gaap_RealizedInvestmentGainsLosses	$ (0.6)us-gaap_RealizedInvestmentGainsLosses	$ 6.4us-gaap_RealizedInvestmentGainsLosses

The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.3(a))

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 325

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6485959&loc=d3e22529-158502

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 3

-Subparagraph a

-Article 7

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Balance Type:	credit
Period Type:	duration