Amount of transactions with related party during the financial reporting period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

Name:	us-gaap_RelatedPartyTransactionAmountsOfTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Related Party Transaction (Details) - USD ($)	1 Months Ended
Related Party Transaction (Details) - USD ($)	Jun. 30, 2016	Mar. 27, 2018
Recovery of short-swing profit
Related Party Transaction [Line Items]
Recovery of related party short-swing profits	$ 900,000
2.50% Convertible notes due 2023 \| Unsecured obligations
Related Party Transaction [Line Items]
Aggregate principal amount		$ 150,000,000
2.50% Convertible notes due 2023 \| Unsecured obligations \| Company affiliates with a member of the board
Related Party Transaction [Line Items]
Aggregate principal amount		$ 30,000,000