Long-term Debt (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Total debt including current maturities	$ 599,558	$ 939,391
Current maturities	(350,005)	(41)
Total long-term debt	249,553	939,350
6.375% notes, due 2012, net of unamortized discount of $38
Debt Instrument [Line Items]
Notes payable	349,962	349,846
7.05% notes, due 2029, net of unamortized discount of $1,616
Debt Instrument [Line Items]
Notes payable	248,384	248,291
Notes payable to banks, 0.7375%
Debt Instrument [Line Items]
Notes payable	0	340,000
Other, 6%, due through 2028
Debt Instrument [Line Items]
Notes payable	$ 1,212	$ 1,254