Long-term Debt- 2015 Senior PIK Toggle Notes (Details) - Senior notes - Senior PIK Toggle Notes due May 2020 - USD ($)	Jul. 31, 2016	May 31, 2015
Debt Instrument [Line Items]
Amount of debt issued		$ 550,000,000.0
Cash interest rate (as percent)	8.75%	8.75%
PIK interest rate (as percent)	9.50%	9.50%

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

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=34725769&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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