Convertible Senior Debt (Details) - USD ($)	Jun. 30, 2015	Dec. 31, 2014
Schedule of convertible senior debt
Convertible senior debt	$ 411,194,000	$ 700,000,000
Convertible Senior Notes [Member]
Schedule of convertible senior debt
Convertible senior debt	$ 411,194,000	$ 700,000,000
Convertible Senior Notes [Member] \| Notes due 2016 [Member]
Schedule of convertible senior debt
Interest Rate	5.00%	5.00%
Convertible senior debt	$ 9,519,000	$ 50,000,000
Convertible Senior Notes [Member] \| Notes due 2018 [Member]
Schedule of convertible senior debt
Interest Rate	4.25%	4.25%
Convertible senior debt	$ 229,913,000	$ 350,000,000
Convertible Senior Notes [Member] \| Notes due 2020 [Member]
Schedule of convertible senior debt
Interest Rate	3.625%	3.625%
Convertible senior debt	$ 171,762,000	$ 300,000,000

Including the current and noncurrent portions, the carrying value of convertible subordinated debt, as of the balance sheet date, initially scheduled to be repaid after one year or beyond the normal operating cycle if longer. This form of debt can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder, and places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

Reference 1: 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)

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX210.5-02.22))

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

Reference 3: 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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Article 5

-Subsection 20, 22

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

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