Debt Issuance - Additional Information (Detail) - USD ($)	Aug. 28, 2015	Jun. 16, 2015	Aug. 01, 2015	Apr. 25, 2015
Line of Credit Facility [Line Items]
Credit facility, borrowed amount			$ 0	$ 0
Credit Agreement [Member]
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity		$ 1,500,000,000
Credit facility, expiration date		Jun. 16, 2020
LIBOR [Member] | Minimum [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
Credit facility, basis spread rate		1.125%
LIBOR [Member] | Maximum [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
Credit facility, basis spread rate		2.00%
Unsecured Term Loan [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity		$ 1,000,000,000
Credit facility, borrowed amount		1,000,000,000
Unsecured Term Loan [Member] | Subsequent Event [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
Credit facility, borrowed amount	$ 1,000,000,000
Credit facility, amount repaid	$ 670,000,000
Unsecured Revolving Line of Credit [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity		500,000,000
Credit facility, borrowed amount		200,000,000
Credit Facility Expiring on December 2016 [Member]
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity		$ 300,000,000