Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Significant Accounting Policies (Details 5) (USD $) In Millions, unless otherwise specified	9 Months Ended	1 Months Ended
	Sep. 30, 2012 item	Aug. 31, 2012 2 3/4 percent Convertible Senior Notes due 2019	Sep. 30, 2012 2 3/4 percent Convertible Senior Notes due 2019	Sep. 30, 2012 2 5/8 percent convertible subordinated notes due 2027
Long-term obligations
Interest rate on convertible debt (as a percent)			2.75%	2.625%
Debt issued		$ 201.3
Segment information
Number of operating segments	1