Investment in TRIP Holdings (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Investment in TRIP Holdings [Abstract]
Capital contributions	$ 47.3	$ 47.3
Equity purchased from investors	44.8	44.8
Total investment	92.1	92.1
Equity in earnings	12.0	7.5
Equity in unrealized losses on derivative financial instruments	(1.3)	(1.4)
Distributions	(7.0)	(7.0)
Deferred broker fees	(0.6)	(0.8)
Carrying Value of TRIP Holdings	$ 95.2	$ 90.4

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6382870&loc=d3e33749-111570

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant