Fair Value (Detail) - Annual Fair Value Measurements of Pension Plan Asses - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value [Line Items]
Pension plan assets		$ 64,903	$ 72,193	$ 74,370
Mutual Funds
Fair Value [Line Items]
Pension plan assets	[1]	23,061	25,499
U.S. Government and Government Agency Securities
Fair Value [Line Items]
Pension plan assets		12,404	15,942
Corporate Bonds
Fair Value [Line Items]
Pension plan assets		9,569	6,599
Common Stock
Fair Value [Line Items]
Pension plan assets		11,330	14,149
Common Trust Funds
Fair Value [Line Items]
Pension plan assets		8,539	10,004
Level 1
Fair Value [Line Items]
Pension plan assets		41,257	47,527
Level 1 | Mutual Funds
Fair Value [Line Items]
Pension plan assets	[1]	23,061	25,499
Level 1 | U.S. Government and Government Agency Securities
Fair Value [Line Items]
Pension plan assets		6,866	7,879
Level 1 | Corporate Bonds
Fair Value [Line Items]
Pension plan assets		0	0
Level 1 | Common Stock
Fair Value [Line Items]
Pension plan assets		11,330	14,149
Level 1 | Common Trust Funds
Fair Value [Line Items]
Pension plan assets		0	0
Level 2
Fair Value [Line Items]
Pension plan assets		23,646	24,666
Level 2 | Mutual Funds
Fair Value [Line Items]
Pension plan assets	[1]	0	0
Level 2 | U.S. Government and Government Agency Securities
Fair Value [Line Items]
Pension plan assets		5,538	8,063
Level 2 | Corporate Bonds
Fair Value [Line Items]
Pension plan assets		9,569	6,599
Level 2 | Common Stock
Fair Value [Line Items]
Pension plan assets		0	0
Level 2 | Common Trust Funds
Fair Value [Line Items]
Pension plan assets		$ 8,539	$ 10,004

[1] Includes mutual funds, money market funds, cash, cash equivalents, and accrued interest.