Summary of Significant Accounting Policies - Summary of Carrying Amounts and Fair Values of Financial Instruments (Parenthetical) (Detail) - Long Term Debt	Sep. 30, 2019
7.50% Senior Notes due 2025
Fair Value Option Quantitative Disclosures [Line Items]
Interest rate on debt instrument	7.50%
9.75% Senior Notes due 2026
Fair Value Option Quantitative Disclosures [Line Items]
Interest rate on debt instrument	9.75%

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant