Fair Value Measurements (Narrative) (Details)	Sep. 30, 2013	Dec. 31, 2012
7.5% Senior Notes due 2018 [Member]
Debt instrument , interest rate percentage	7.50%
Yield, Publicly-traded debt market	2.80%	2.60%
4.10% Senior Notes Due 2022 [Member]
Debt instrument , interest rate percentage	4.10%
Yield, Publicly-traded debt market	4.00%

Contractual interest rate for funds borrowed, under the debt agreement.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

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

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant