Subsequent Event - Additional Information (Detail) (USD $)	9 Months Ended		1 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 Revolving Credit Facility	Oct. 25, 2013 Subsequent Event Loans Payable	Oct. 25, 2013 Subsequent Event Revolving Credit Facility
Subsequent Event [Line Items]
New long term loan obtained			$ 900,000,000
Long term loan, maturity date			2018-10
Scheduled annual principal payments			90,000,000
First principal payments date			Dec. 31, 2014
Revolving credit facility with a syndicate of banks	2,000,000,000
Revolving credit facility, Amended expiration month and year				2018-10
Revolving credit facility, Previous expiration date	Aug. 01, 2017
Borrowing Outstanding	$ 1,000,000,000	$ 75,000,000