Schedule I - Parent Company Financial Information (Condensed Balance Sheets) (Parenthetical) (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Preferred stock, par	$ 1	$ 1
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, issued	0	0
Common stock, par	$ 0.1667	$ 0.1667
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	194,470,820	193,230,310
Treasury stock, shares	36,138,955	29,225,996
Parent Company
Condensed Financial Statements, Captions [Line Items]
Preferred stock, par	$ 1	$ 1
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, issued	0	0
Common stock, par	$ 0.1667	$ 0.1667
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	194,470,820	193,230,310
Treasury stock, shares	36,138,955	29,225,996