Financial Instruments and Fair Value Measurements - Derivative Activity (Parenthetical) (Detail)	12 Months Ended		12 Months Ended
	Dec. 31, 2012 USD ($) Contract	Dec. 31, 2011 USD ($)	Dec. 31, 2012 NAIF II [Member] USD ($) Contract	Dec. 31, 2012 Interest Rate Swap [Member] USD ($)	Sep. 30, 2010 Interest Rate Swap [Member] JPY (¥)
Derivative [Line Items]
Number of interest rate contracts entered into	4		1
Combined notional amount of interest rate swap contracts	$ 445,400,000,000	$ 1,300,000,000	$ 71,000,000	$ 703,800,000
Maturity date of interest rate swap contracts	Various expiration dates between 2017 and 2019
Notional amount of cash flow hedge instruments					¥ 13,000,000,000