Treasury - Additional Information (Detail)				3 Months Ended					12 Months Ended
	Nov. 26, 2018 USD ($)	Oct. 23, 2018 USD ($)	Jun. 07, 2016 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2015 USD ($) Derivative	Sep. 30, 2015 USD ($) Derivative	Jun. 30, 2015 USD ($) Derivative	Dec. 31, 2015 USD ($) Derivative	Dec. 31, 2018 USD ($)	Oct. 31, 2018 USD ($)	Sep. 30, 2018	Jun. 03, 2016 USD ($)	Aug. 07, 2014 USD ($)
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, starting date				Oct. 23, 2018
Rate adjustment to weighted average federal funds rate for credit facility borrowings				0.50%
Rate adjustment to one month Eurodollar rate on credit facility borrowings				1.00%
Accounts receivable securitization program credit facility, borrowing capacity				$ 450,000,000	$ 440,000,000
Accounts receivable securitization program credit facility, amount outstanding				290,000,000
Accounts receivable securitization program credit facility, available borrowing capacity				160,000,000
Debt instrument carrying amount				3,900,000,000						$ 4,000,000,000
Fair value of debt				3,900,000,000						$ 4,000,000,000
Number of additional forward starting interest rate swaps | Derivative							4
One Point Three One Percent Forward Starting Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Number of additional forward starting interest rate swaps | Derivative									9
Maturity date of interest rate cash flow hedges									Apr. 15, 2019
Fixed rate payable on interest rate swap						1.31%			1.31%
One Point Four Zero Percent Forward Starting Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Number of additional forward starting interest rate swaps | Derivative								4,000,000
Maturity date of interest rate cash flow hedges								Apr. 15, 2019
Average fixed rate payable on interest rate swap								1.40%
Forward Starting Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Maturity date of interest rate cash flow hedges							Apr. 15, 2019
Average fixed rate payable on interest rate swap							1.23%
One Point Two One Percent Forward Starting Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Number of additional forward starting interest rate swaps | Derivative						1
Maturity date of interest rate cash flow hedges						Apr. 15, 2019
Fixed rate payable on interest rate swap						1.21%			1.21%
Foreign Currency Forward Exchange Contracts
Equity Class Of Treasury Stock [Line Items]
Net cash inflows (outflows)				13,000,000	$ (46,000,000)
Cash Flow Hedging | One Point Three One Percent Forward Starting Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Notional amount of interest rate cash flow hedges						$ 1,000,000,000			$ 1,000,000,000
Cash Flow Hedging | One Point Four Zero Percent Forward Starting Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Notional amount of interest rate cash flow hedges								$ 500,000,000
Cash Flow Hedging | Forward Starting Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Notional amount of interest rate cash flow hedges							$ 400,000,000
Cash Flow Hedging | One Point Two Three Percent Forward Starting Interest Rate Swaps One
Equity Class Of Treasury Stock [Line Items]
Notional amount of interest rate cash flow hedges							100,000,000
Cash Flow Hedging | One Point Two Three Percent Forward Starting Interest Rate Swaps Two
Equity Class Of Treasury Stock [Line Items]
Notional amount of interest rate cash flow hedges							200,000,000
Cash Flow Hedging | One Point Two Three Percent Forward Starting Interest Rate Swaps Three
Equity Class Of Treasury Stock [Line Items]
Notional amount of interest rate cash flow hedges							$ 100,000,000
Cash Flow Hedging | One Point Two One Percent Forward Starting Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Notional amount of interest rate cash flow hedges						$ 100,000,000			$ 100,000,000
Revolving Credit Facility
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, borrowing capacity		$ 1,000,000,000	$ 800,000,000	1,000,000,000
Line of credit facility increased amount		200,000,000
Line of credit facility, available borrowing capacity				973,000,000
Line of credit facility amount outstanding				$ 0
Current applicable margins				1.50%
Revolving Credit Facility | ABR-based loans
Equity Class Of Treasury Stock [Line Items]
Current applicable margins				0.50%
Revolving Credit Facility | Minimum | One Month Eurodollar Rate Plus Index Based Loans
Equity Class Of Treasury Stock [Line Items]
Consolidated Leverage Ratio				0.375%
Revolving Credit Facility | Minimum | One Two Three Six Month Eurodollar Rate Plus Index Based Loans
Equity Class Of Treasury Stock [Line Items]
Consolidated Leverage Ratio				1.375%
Revolving Credit Facility | Maximum | One Month Eurodollar Rate Plus Index Based Loans
Equity Class Of Treasury Stock [Line Items]
Consolidated Leverage Ratio				0.625%
Revolving Credit Facility | Maximum | One Two Three Six Month Eurodollar Rate Plus Index Based Loans
Equity Class Of Treasury Stock [Line Items]
Consolidated Leverage Ratio				1.625%
Revolving Credit Facility | Short Term on Demand Credit Facility
Equity Class Of Treasury Stock [Line Items]
Line of credit facility amount outstanding				$ 15,000,000
Revolving Credit Facility | Letter of Credit
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, borrowing capacity				125,000,000
Line of credit facility amount outstanding				12,000,000
Tranche A Term Loan
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, borrowing capacity		2,000,000,000	$ 1,710,000,000
Line of credit facility increased amount		$ 290,000,000
Senior notes, maturity date		Oct. 23, 2023	Aug. 07, 2019
Line of credit facility amount outstanding				1,988,000,000
Tranche A Term Loan | Quarterly Payment for First Eight Installments
Equity Class Of Treasury Stock [Line Items]
Scheduled principal payments per quarter				$ 12,500,000
Debt Instrument Periodic Payment, description				covering the period of March of 2019 through December of 2020
Tranche A Term Loan | Quarterly Payment after Eight Installments Until Maturity
Equity Class Of Treasury Stock [Line Items]
Scheduled principal payments per quarter				$ 25,000,000
Debt Instrument Periodic Payment, description				commencing in March of 2021 until maturity in October of 2023
Tranche B Term Loan
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, borrowing capacity											$ 500,000,000
Senior notes, maturity date				Oct. 31, 2025
Line of credit facility amount outstanding				$ 499,000,000
Scheduled principal payments per quarter				$ 1,250,000
Debt Instrument Periodic Payment, description				which commenced on March 31, 2019 until maturity in October of 2025
New Senior Secured Notes
Equity Class Of Treasury Stock [Line Items]
Senior notes, issued				$ 1,100,000,000
New Senior Secured Notes | 3.75% Senior Secured Notes due 2019
Equity Class Of Treasury Stock [Line Items]
Senior Notes														$ 300,000,000
Senior notes, interest rate														3.75%
Redemption of senior notes	$ 300,000,000
Redemption price, percentage	100.485%
Redemption premium paid	$ 1,000,000
New Senior Secured Notes | 4.75% Senior Secured Notes due 2022
Equity Class Of Treasury Stock [Line Items]
Senior notes, maturity date				Aug. 01, 2022
Senior notes, interest rate				4.75%
Senior notes, issued				$ 700,000,000
New Senior Secured Notes | 4.75% Senior Secured Notes due 2022 | Senior Secured Notes Issued on August Seven Two Thousand Fourteen
Equity Class Of Treasury Stock [Line Items]
Senior notes, issued				300,000,000
New Senior Secured Notes | 4.75% Senior Secured Notes due 2022 | Senior Secured Notes Issued on June Three Two Thousand Sixteen
Equity Class Of Treasury Stock [Line Items]
Senior notes, issued				$ 400,000,000
Senior notes issued percentage				101.50%
Senior notes yield percentage				4.35%
New Senior Secured Notes | 5.00% Senior Secured Notes due 2026
Equity Class Of Treasury Stock [Line Items]
Senior notes, maturity date				Jun. 01, 2026
New Senior Secured Notes | 5.00% Senior Secured Notes due 2026 | Senior Secured Notes Issued on June Three Two Thousand Sixteen
Equity Class Of Treasury Stock [Line Items]
Senior notes, interest rate													5.00%
Senior notes, issued													$ 400,000,000
Term Loan A
Equity Class Of Treasury Stock [Line Items]
Current applicable margins				1.50%
Term Loan A | ABR-based loans
Equity Class Of Treasury Stock [Line Items]
Current applicable margins				0.50%
Term Loan A | Minimum | One Month Eurodollar Rate Plus Index Based Loans
Equity Class Of Treasury Stock [Line Items]
Consolidated Leverage Ratio												0.375%
Term Loan A | Minimum | One Two Three Six Month Eurodollar Rate Plus Index Based Loans
Equity Class Of Treasury Stock [Line Items]
Consolidated Leverage Ratio				1.375%
Term Loan A | Maximum | One Month Eurodollar Rate Plus Index Based Loans
Equity Class Of Treasury Stock [Line Items]
Consolidated Leverage Ratio												0.625%
Term Loan A | Maximum | One Two Three Six Month Eurodollar Rate Plus Index Based Loans
Equity Class Of Treasury Stock [Line Items]
Consolidated Leverage Ratio				1.625%
Term Loan A | Tranche B Term Loan | One Month Eurodollar Rate Plus Index Based Loans
Equity Class Of Treasury Stock [Line Items]
Consolidated Leverage Ratio				0.75%
Term Loan A | Tranche B Term Loan | One Two Three Six Month Eurodollar Rate Plus Index Based Loans
Equity Class Of Treasury Stock [Line Items]
Consolidated Leverage Ratio				1.75%