Debt and Credit Facilities - Additional Information (Detail) - 3 months ended Jun. 30, 2015 - USD ($) $ in Millions	Total
5.50% Senior Notes due September 2025 [Member]
Debt Instrument [Line Items]
Credit facility, maturity date	Sep. 15, 2025
Non-lender fees	$ 8
4.50% Senior Notes due September 2023 [Member]
Debt Instrument [Line Items]
Credit facility, maturity date	Sep. 15, 2023
Non-lender fees	$ 8
8.375% Senior Notes Due September 2021 [Member]
Debt Instrument [Line Items]
Credit facility, maturity date	Sep. 01, 2021
Aggregate repurchase price of senior notes	$ 866
Premium paid on redemption of debt	99
Accrued interest paid on redemption of debt	17
Amortization Of Debt Discount Premium	$ 11

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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