Debt - Fair Value Of Embedded Derivatives (Details) - Notes - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair value of 2033 Senior Notes:
With the embedded derivatives	$ 36,526
Without the embedded derivatives	29,804
Estimated fair value of the embedded derivatives	$ 6,722	$ 16,736

Fair value as of the balance sheet date of the embedded derivative or group of embedded derivatives classified as a liability.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

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