Stock Transactions and Unit Redemptions - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended	3 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013 Global Partnership Restructuring Program [Member]	Sep. 30, 2013 Global Partnership Restructuring Program [Member]	Jul. 30, 2013 Class A Common Stock [Member]	Sep. 30, 2013 Class A Common Stock [Member]	Dec. 31, 2012 Class A Common Stock [Member]	Sep. 30, 2013 Class A Common Stock [Member] Controlled Equity Offerings [Member]
Class of Stock [Line Items]
Payment percentage of the gross proceeds from the sale of shares	2.00%
Maximum number of shares under the controlled equity offering					20,000,000
Common stock, shares issued					197,924,000	141,955,000	9,050,010
Company's repurchase and additional redemption authority amount				$ 250
Redemption of partner units		77,000,000	77,000,000
Common stock granted		45,000,000			2,453,473	4,797,177
Common stock issued, restricted shares		39,000,000	39,000,000