Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 3: 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_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Borrowings - Components of Long-term Borrowings (Parenthetical) (Detail)			9 Months Ended	12 Months Ended
	Jan. 17, 2017	Jul. 18, 2013	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
5.0% Exchangeable Senior Notes due March 2021 [Member] \| Exchangeable Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	5.00%		5.00%	5.00%	5.00%
Due date	Mar. 01, 2021		Mar. 01, 2021	Mar. 01, 2021
6.625% Senior Notes Due July 2021 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate		6.625%	6.625%	6.625%
Due date		Jul. 15, 2021	Jul. 01, 2021	Jul. 01, 2021