Debt - Debt Summary (Parenthetical) (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Jun. 30, 2013 Exchangeable Senior Notes [Member]	Sep. 30, 2013 Exchangeable Senior Notes [Member]	Dec. 31, 2012 Exchangeable Senior Notes [Member]	Sep. 30, 2013 Euro [Member]	Sep. 30, 2013 Japanese Yen [Member]
Schedule Of Long Term Debt [Line Items]
Foreign principal borrowing included in total debt denominated in non-U.S. dollars					$ 1,400,000,000	$ 500,000,000
Weighted average coupon interest rate			3.30%	2.80%
Repayment of exchangeable senior notes		342,200,000
Interest rate of exchangeable note			3.30%
Repayment of outstanding secured mortgage debt	1,400,000,000
Debt transferred to PELP	$ 353,200,000