Financing Arrangements - Additional Information (Detail)	Jun. 30, 2018 DebtFinancing	Jun. 29, 2018 USD ($)	Dec. 31, 2017 DebtFinancing
Debt Instrument [Line Items]
Number of debt financing | DebtFinancing	0		0
Merger Sub [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Issued aggregate principal amount		$ 1,700,000,000
Merger Sub [Member] | Senior Notes [Member] | Notes due 2023 [Member]
Debt Instrument [Line Items]
Issued aggregate principal amount		$ 950,000,000
Stated interest rate		8.125%
Merger Sub [Member] | Senior Notes [Member] | Notes due 2026 [Member]
Debt Instrument [Line Items]
Issued aggregate principal amount		$ 750,000,000
Stated interest rate		9.125%