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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031898-161870

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Earnings Per Share - Narratives (Details) - Convertible Notes, due 2024 - Convertible Debt - $ / shares	Dec. 31, 2017	Nov. 06, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share
Debt instrument, conversion price (usd per share)		$ 58.725
Maximum
Antidilutive Securities Excluded from Computation of Earnings Per Share
Debt instrument, conversion price (usd per share)	$ 71.775