The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Name:	us-gaap_UnrealizedGainLossOnDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Fair Value Measurements Fair Value Measurements, Textual (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Minimum	Jun. 30, 2014 Maximum	Jun. 30, 2014 Derivative	Dec. 31, 2013 Derivative
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Net Asset (Liability)					$ 0.6	$ (4.3)
Non-cash unrealized (gains) losses on derivative positions	$ 4.9	$ (5.4)
Short-term investment maturity period			32 days	9 months