Debt - Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term debt	$ 1,415,700	$ 1,061,000
Less: current portion of long-term debt	(292,795)	0
Long-term debt	$ 1,122,945	$ 1,060,955
1.75% Senior Notes due 2017
Debt Instrument [Line Items]
Interest rate		1.75%
1.75% Senior Notes due 2017 \| Convertible Debt
Debt Instrument [Line Items]
Interest rate	1.75%
Long-term debt	$ 292,400	$ 279,300
7 1⁄2% Senior Notes due 2022
Debt Instrument [Line Items]
Interest rate		7.50%
7 1⁄2% Senior Notes due 2022 \| Senior Notes
Debt Instrument [Line Items]
Interest rate	7.50%
Long-term debt	$ 770,400	$ 770,000
4.20% Building Loan
Debt Instrument [Line Items]
Interest rate		4.20%
4.20% Building Loan \| Secured Debt
Debt Instrument [Line Items]
Interest rate	4.20%
Long-term debt	$ 11,400	$ 11,700
Revolving Credit Facility \| Revolving credit facility \| Line of Credit
Debt Instrument [Line Items]
Long-term debt	$ 341,500	$ 0

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

Reference 1: 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

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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(a)(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 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 FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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+ References

Reference 1: 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)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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