Summary of SERP Assets Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
SERP assets measured at fair value on a recurring basis	$ 35	$ 5
Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
SERP assets measured at fair value on a recurring basis	1,956	2,103
Level 1 | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
SERP assets measured at fair value on a recurring basis	0	0
Level 1 | Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
SERP assets measured at fair value on a recurring basis	0	0
Level 2 | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
SERP assets measured at fair value on a recurring basis	35	5
Level 2 | Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
SERP assets measured at fair value on a recurring basis	1,956	2,103
Level 3 | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
SERP assets measured at fair value on a recurring basis	0	0
Level 3 | Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
SERP assets measured at fair value on a recurring basis	$ 0	$ 0