Fair Values of Pension Plan Assets by Asset Category and by Level (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	$ 69,032	$ 61,334
Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	243	26
U.S. large value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	3,801	3,210
U.S. large growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	3,731	3,020
U.K. index
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets		6,507
International large value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	986	9,151
International blend
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	5,629	4,669
International growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	2,866	2,498
Emerging Markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	2,516	2,353
Balanced
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	20,666	2,801
Government Bond Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets		4,063
Corporate Bond Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	18,984	14,693
U.S. property
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	6,767	5,968
U.K. property
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	2,843	2,375
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	13,157	11,107
Level 1 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	243	26
Level 1 | U.S. large value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	3,801	3,210
Level 1 | U.S. large growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	3,731	3,020
Level 1 | International growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	2,866	2,498
Level 1 | Emerging Markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	2,516	2,353
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	46,265	41,884
Level 2 | U.K. index
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets		6,507
Level 2 | International large value
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	986	9,151
Level 2 | International blend
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	5,629	4,669
Level 2 | Balanced
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	20,666	2,801
Level 2 | Government Bond Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets		4,063
Level 2 | Corporate Bond Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	18,984	14,693
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	9,610	8,343	6,210
Level 3 | U.S. property
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	6,767	5,968
Level 3 | U.K. property
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plans assets	$ 2,843	$ 2,375