Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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

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

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

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- Definition

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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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The carrying value as of the balance sheet date of the current portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 210
-Section S99
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Debt - Additional Information (Details) - USD ($)	9 Months Ended
Debt - Additional Information (Details) - USD ($)	Sep. 30, 2017	Jun. 06, 2017	Jan. 31, 2017	Dec. 31, 2016	Nov. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
1.125% Convertible Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate on Notes	1.125%
Letter of Credit
Debt Instrument [Line Items]
Amount outstanding under Letter of Credit	$ 6,000,000
Letter of Credit \| Debt Commitment Letter
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 400,000,000
Senior Notes \| 4.875% Notes
Debt Instrument [Line Items]
Face amount of debts		$ 330,000,000
Percentage of contractual interest rate on Notes	4.875%	4.875%
Senior Notes \| 5.375% Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate on Notes	5.375%				5.375%
Aggregate principal amount of notes outstanding	$ 700,000,000
Unsecured Debt \| Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 500,000,000
Current borrowing capacity	$ 194,000,000
Term of debt instrument	5 years
Amount outstanding under the Credit Facility	$ 300,000,000
Convertible Notes \| 1.125% Convertible Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate on Notes	1.125%			1.125%			1.125%
Aggregate principal amount of notes outstanding	$ 550,000,000
Conversion price per share of common stock (in dollars per share)	$ 53.00
Convertible Notes \| 1.625% Convertible Notes
Debt Instrument [Line Items]
Percentage of contractual interest rate on Notes	1.625%					1.625%
Aggregate principal amount of notes outstanding	$ 302,000,000
Conversion price per share of common stock (in dollars per share)	$ 75.51