Debt (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Debt Disclosure [Abstract]
Carrying Amount, 6.35% Senior Notes, $ 200 million par value, maturing April 2016	$ 204,028	$ 205,754
Carrying Amount, Capital leases	12,215	11,837
Carrying Amount, Total debt	216,243	217,591
Carrying Amount, Less current maturities	(2,428)	(2,208)
Carrying Amount, Long-term debt	213,815	215,383
Estimated Fair Value, 6.35% Senior Notes, $ 200 million par value, maturing April 2016	218,750	219,500
Estimated Fair Value, Capital leases	12,215	11,837
Estimated Fair Value, Total debt	230,965	231,337
Estimated Fair Value, Less current maturities	(2,428)	(2,208)
Estimated Fair Value, Long-term debt	$ 228,537	$ 229,129