Accumulated Other Comprehensive Loss, Net of Tax (Parenthetical) (Detail) (USD $)	Sep. 30, 2011	Dec. 31, 2010
Unrealized losses on temporarily impaired investments, tax benefits	$ (16,732,000)	$ (7,278,000)
Unrealized gains on investments, taxes	16,605,000	32,684,000
Unrealized gains (losses) on derivatives, taxes (benefits)	(55,355,000)	(3,403,000)
Recognition of actuarial net loss from pension and other postretirement plans, tax benefits	$ (70,388,000)	$ (70,388,000)