Treasury - Additional Information (Detail) $ in Thousands				3 Months Ended			9 Months Ended		12 Months Ended
	Oct. 31, 2018 USD ($)	Oct. 23, 2018 USD ($)	May 31, 2015 USD ($) Derivative	Dec. 31, 2015 USD ($) Derivative	Sep. 30, 2015 USD ($) Derivative	Jun. 30, 2015 USD ($) Derivative	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2015 USD ($) Derivative	Jun. 30, 2018	Apr. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	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	$ 440,000
Accounts receivable securitization program credit facility, amount outstanding							$ 425,000
Accounts receivable securitization program credit facility, available borrowing capacity							25,000
Debt instrument carrying amount							4,000,000						$ 4,000,000
Fair value of debt							4,000,000						4,100,000
Number of additional forward starting interest rate swaps | Derivative					4
Previously Outstanding Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Maturity date of interest rate cash flow hedges			May 31, 2015
One Point Three One Percent Forward Starting Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Maturity date of interest rate cash flow hedges									Apr. 15, 2019
Number of additional forward starting interest rate swaps | Derivative									9
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]
Maturity date of interest rate cash flow hedges						Apr. 15, 2019
Number of additional forward starting interest rate swaps | Derivative						4
Average fixed rate payable on interest rate swap						1.40%
One Point Two Three Percent Forward Starting Interest Rate Swaps One
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]
Maturity date of interest rate cash flow hedges				Apr. 15, 2019
Number of additional forward starting interest rate swaps | Derivative				1
Fixed rate payable on interest rate swap				1.21%					1.21%
Interest Rate Swap
Equity Class Of Treasury Stock [Line Items]
Fair value of our interest rate swaps													7,000
Interest Rate Swap | Net Accounts Receivable
Equity Class Of Treasury Stock [Line Items]
Fair value of our interest rate swaps, assets							6,000						4,000
Interest Rate Swap | Other Assets
Equity Class Of Treasury Stock [Line Items]
Fair value of our interest rate swaps, assets													$ 3,000
Foreign Currency Forward Exchange Contracts
Equity Class Of Treasury Stock [Line Items]
Net cash inflows (outflows)							26,000	$ (72,000)
Cash Flow Hedging | Previously Outstanding Interest Rate Swaps
Equity Class Of Treasury Stock [Line Items]
Number of interest rate swaps | Derivative			7
Notional amount of interest rate cash flow hedges			$ 825,000
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					$ 1,000,000
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
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
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
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
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
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					$ 100,000
Revolving Credit Facility
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, borrowing capacity							800,000
Line of credit facility, available borrowing capacity							282,000
Line of credit facility amount outstanding							$ 480,000
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							$ 4,000
Revolving Credit Facility | Letter of Credit
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, borrowing capacity							125,000
Letters of credit, outstanding							34,000
Tranche A Term Loan
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, borrowing capacity							$ 1,710,000
Senior notes, maturity date							Aug. 07, 2019
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%
New Senior Secured Notes
Equity Class Of Treasury Stock [Line Items]
Senior notes, issued							$ 1,400,000
New Senior Secured Notes | 3.75% Senior Secured Notes due 2019
Equity Class Of Treasury Stock [Line Items]
Senior notes, maturity date							Aug. 01, 2019
Senior notes, issued															$ 300,000
Senior notes, interest rate															3.75%
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, issued							$ 700,000							$ 400,000	$ 300,000
Senior notes, interest rate							4.75%
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
Senior notes, issued														$ 400,000
Senior notes, interest rate														5.00%
Subsequent Event | Revolving Credit Facility
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, borrowing capacity		$ 1,000,000
Line of credit facility increased amount		200,000
Subsequent Event | Tranche A Term Loan
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, borrowing capacity		2,000,000
Line of credit facility increased amount		$ 290,000
Senior notes, maturity date		Oct. 23, 2023
Debt Instrument Periodic Payment Commencing Date	Mar. 31, 2019
Subsequent Event | Tranche A Term Loan | Quarterly Payment for First Eight Installments
Equity Class Of Treasury Stock [Line Items]
Scheduled principal payments made	$ 12,500
Subsequent Event | Tranche A Term Loan | Quarterly Payment after Eight Installments Until Maturity
Equity Class Of Treasury Stock [Line Items]
Scheduled principal payments made	25,000
Subsequent Event | Tranche B Term Loan
Equity Class Of Treasury Stock [Line Items]
Line of credit facility, borrowing capacity	$ 500,000
Senior notes, maturity date	Oct. 31, 2025
Scheduled principal payments made	$ 1,250
Debt Instrument Periodic Payment Commencing Date	Mar. 31, 2019