Net Income Per Share (Narrative) (Details) - Convertible Debt	Mar. 31, 2017 $ / shares
2.50% Convertible Senior Notes, Due April 1, 2021 (2.50% Notes)
Debt Instrument [Line Items]
Conversion price (in usd per share)	$ 16.77
Stated interest rate (as a percent)	2.50%
2.0% Convertible Senior Notes due August 15, 2021
Debt Instrument [Line Items]
Conversion price (in usd per share)	$ 20.41
Stated interest rate (as a percent)	2.00%

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

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)
-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031898-161870

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- Definition

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

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

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- Definition

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.

+ References

No definition available.

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