Benefit Plans - Fair Value Measurement (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments	100.00%	100.00%
Investments:
Investments, Fair Value Disclosure	$ 184,206	$ 138,331
Equity securities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments	42.00%	49.00%
Investments:
Investments, Fair Value Disclosure	77,565	67,653
Corporate bonds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments	23.00%	20.00%
Investments:
Investments, Fair Value Disclosure	41,863	28,153
Mutual funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments	18.00%	10.00%
Investments:
Investments, Fair Value Disclosure	33,690	13,545
U.S. Treasury securities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments	10.00%	10.00%
Investments:
Investments, Fair Value Disclosure	19,057	13,249
Cash and money market funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments	5.00%	9.00%
Investments:
Investments, Fair Value Disclosure	9,939	12,355
U.S. government agency securities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments	1.00%	1.00%
Investments:
Investments, Fair Value Disclosure	1,896	1,615
Trust preferred securities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments	1.00%	1.00%
Investments:
Investments, Fair Value Disclosure	196	1,761
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Investments:
Investments, Fair Value Disclosure	140,447	108,563
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity securities [Member]
Investments:
Investments, Fair Value Disclosure	77,565	67,653
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate bonds [Member]
Investments:
Investments, Fair Value Disclosure
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mutual funds [Member]
Investments:
Investments, Fair Value Disclosure	33,690	13,545
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury securities [Member]
Investments:
Investments, Fair Value Disclosure	19,057	13,249
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash and money market funds [Member]
Investments:
Investments, Fair Value Disclosure	9,939	12,355
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. government agency securities [Member]
Investments:
Investments, Fair Value Disclosure
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Trust preferred securities [Member]
Investments:
Investments, Fair Value Disclosure	196	1,761
Significant Other Observable Inputs (Level 2) [Member]
Investments:
Investments, Fair Value Disclosure	43,759	29,768
Significant Other Observable Inputs (Level 2) [Member] | Equity securities [Member]
Investments:
Investments, Fair Value Disclosure
Significant Other Observable Inputs (Level 2) [Member] | Corporate bonds [Member]
Investments:
Investments, Fair Value Disclosure	41,863	28,153
Significant Other Observable Inputs (Level 2) [Member] | Mutual funds [Member]
Investments:
Investments, Fair Value Disclosure
Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury securities [Member]
Investments:
Investments, Fair Value Disclosure
Significant Other Observable Inputs (Level 2) [Member] | Cash and money market funds [Member]
Investments:
Investments, Fair Value Disclosure
Significant Other Observable Inputs (Level 2) [Member] | U.S. government agency securities [Member]
Investments:
Investments, Fair Value Disclosure	1,896	1,615
Significant Other Observable Inputs (Level 2) [Member] | Trust preferred securities [Member]
Investments:
Investments, Fair Value Disclosure
Significant Unobservable Inputs (Level 3) [Member]
Investments:
Investments, Fair Value Disclosure
Significant Unobservable Inputs (Level 3) [Member] | Equity securities [Member]
Investments:
Investments, Fair Value Disclosure
Significant Unobservable Inputs (Level 3) [Member] | Corporate bonds [Member]
Investments:
Investments, Fair Value Disclosure
Significant Unobservable Inputs (Level 3) [Member] | Mutual funds [Member]
Investments:
Investments, Fair Value Disclosure
Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury securities [Member]
Investments:
Investments, Fair Value Disclosure
Significant Unobservable Inputs (Level 3) [Member] | Cash and money market funds [Member]
Investments:
Investments, Fair Value Disclosure
Significant Unobservable Inputs (Level 3) [Member] | U.S. government agency securities [Member]
Investments:
Investments, Fair Value Disclosure
Significant Unobservable Inputs (Level 3) [Member] | Trust preferred securities [Member]
Investments:
Investments, Fair Value Disclosure