Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16(a)(2))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_ConvertibleDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Fair Value Measurements (Narrative) (Details) (USD $)	Dec. 31, 2012 8% Series 2000 [Member]	Dec. 31, 2000 8% Series 2000 [Member]	Dec. 31, 2012 1.875% convertible debentures [Member]	Dec. 31, 2009 1.875% convertible debentures [Member]	Mar. 12, 2008 1.875% convertible debentures [Member]	Dec. 31, 2012 1.75% convertible debentures [Member]	Oct. 17, 2012 1.75% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, face amount	$ 30,000,000	$ 30,000,000			$ 181,500,000	$ 396,750,000	$ 396,750,000
Debt instrument, stated rate	8.00%		1.875%			1.75%
Convertible debentures			$ 166,500,000	$ 166,500,000		$ 258,200,000