Fair Value Measurements - Additional Information (Detail)	3 Months Ended
	Dec. 31, 2013 USD ($) Swap	Dec. 31, 2014 USD ($) Swap	Sep. 30, 2014 USD ($) Swap	Dec. 31, 2013 JPY (¥)	Sep. 30, 2014 Unrealized Gains USD ($)	Dec. 31, 2013 Unrealized Gains USD ($)	Dec. 31, 2014 Unrealized Losses USD ($)	Sep. 30, 2014 Unrealized Losses USD ($)	Dec. 31, 2013 Unrealized Losses USD ($)	Dec. 31, 2014 Cross-Currency Interest Rate Swaps JPY (¥) Swap	Sep. 30, 2014 Cross-Currency Interest Rate Swaps JPY (¥) Swap	Dec. 31, 2013 Cross-Currency Interest Rate Swaps JPY (¥) Swap
Derivative [Line Items]
Cross-currency interest rate swaps outstanding				¥ 20,000,000,000						¥ 20,000,000,000	¥ 20,000,000,000	¥ 20,000,000,000
Number Of Cross Currency Interest Rate Swaps Outstanding	4
Unrealized gains (losses) on investments in marketable common stock					0	5,000,000	0	0	0
Fair value of long term debt	6,000,000,000	6,900,000,000	6,800,000,000
Number of Interest Rate Derivatives Held	10	13	13							4	4	4
Proceeds from Sale of Available-for-sale Securities, Equity	3,000,000
Available-for-sale Securities, Gross Realized Gains	$ 1,000,000