Long-Term Debt (Detail) - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term debt	$ 1,052,183,000	$ 1,041,035,000
Convertible Debt [Member] \| 1.75% Senior Notes due 2017 [Member]
Debt Instrument [Line Items]
Long-term debt	277,200,000	266,000,000
Senior Notes [Member] \| 7.5% Notes due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	775,000,000	775,000,000
Bank Debt [Member]
Debt Instrument [Line Items]
Outstanding letters of credit	$ 0	$ 0

Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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