Employee Benefit Plans - Summary of Pension Plan Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	$ 50,384	$ 44,998
Investments in equity securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	26,545	23,373
Investments in equity securities [Member] | U.S. Large Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	6,947	6,297
Investments in equity securities [Member] | U.S. Mid Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	3,078	2,683
Investments in equity securities [Member] | U.S. Small Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	1,523	1,341
Investments in equity securities [Member] | International [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	10,019	8,563
Investments in equity securities [Member] | Alternative Strategies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	4,978	4,489
Debt securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	19,163	17,110
Debt securities [Member] | Inflation Protected [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	2,507	2,237
Debt securities [Member] | Fixed Income [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	14,109	12,617
Debt securities [Member] | High Yield [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	2,547	2,256
Other [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	4,676	4,515
Other [Member] | Commodities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	1,918	1,789
Other [Member] | Real Estate [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	2,048	1,797
Other [Member] | Guaranteed deposit [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	710	897
Other [Member] | Other [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets		32
Quoted Prices in Active Markets (Level 1) [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	24,974	22,053
Quoted Prices in Active Markets (Level 1) [Member] | Investments in equity securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	18,501	16,198
Quoted Prices in Active Markets (Level 1) [Member] | Investments in equity securities [Member] | U.S. Large Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	3,504	3,146
Quoted Prices in Active Markets (Level 1) [Member] | Investments in equity securities [Member] | U.S. Mid Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Quoted Prices in Active Markets (Level 1) [Member] | Investments in equity securities [Member] | U.S. Small Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Quoted Prices in Active Markets (Level 1) [Member] | Investments in equity securities [Member] | International [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	10,019	8,563
Quoted Prices in Active Markets (Level 1) [Member] | Investments in equity securities [Member] | Alternative Strategies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	4,978	4,489
Quoted Prices in Active Markets (Level 1) [Member] | Debt securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	2,507	2,237
Quoted Prices in Active Markets (Level 1) [Member] | Debt securities [Member] | Inflation Protected [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	2,507	2,237
Quoted Prices in Active Markets (Level 1) [Member] | Debt securities [Member] | Fixed Income [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Quoted Prices in Active Markets (Level 1) [Member] | Debt securities [Member] | High Yield [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Quoted Prices in Active Markets (Level 1) [Member] | Other [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	3,966	3,618
Quoted Prices in Active Markets (Level 1) [Member] | Other [Member] | Commodities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	1,918	1,789
Quoted Prices in Active Markets (Level 1) [Member] | Other [Member] | Real Estate [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	2,048	1,797
Quoted Prices in Active Markets (Level 1) [Member] | Other [Member] | Guaranteed deposit [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Quoted Prices in Active Markets (Level 1) [Member] | Other [Member] | Other [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets		32
Significant Other Observable Inputs (Level 2) [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	24,700	22,048
Significant Other Observable Inputs (Level 2) [Member] | Investments in equity securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	8,044	7,175
Significant Other Observable Inputs (Level 2) [Member] | Investments in equity securities [Member] | U.S. Large Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	3,443	3,151
Significant Other Observable Inputs (Level 2) [Member] | Investments in equity securities [Member] | U.S. Mid Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	3,078	2,683
Significant Other Observable Inputs (Level 2) [Member] | Investments in equity securities [Member] | U.S. Small Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	1,523	1,341
Significant Other Observable Inputs (Level 2) [Member] | Investments in equity securities [Member] | International [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Other Observable Inputs (Level 2) [Member] | Investments in equity securities [Member] | Alternative Strategies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Other Observable Inputs (Level 2) [Member] | Debt securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	16,656	14,873
Significant Other Observable Inputs (Level 2) [Member] | Debt securities [Member] | Inflation Protected [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Other Observable Inputs (Level 2) [Member] | Debt securities [Member] | Fixed Income [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	14,109	12,617
Significant Other Observable Inputs (Level 2) [Member] | Debt securities [Member] | High Yield [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	2,547	2,256
Significant Other Observable Inputs (Level 2) [Member] | Other [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Other Observable Inputs (Level 2) [Member] | Other [Member] | Commodities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Other Observable Inputs (Level 2) [Member] | Other [Member] | Real Estate [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Other Observable Inputs (Level 2) [Member] | Other [Member] | Guaranteed deposit [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Other Observable Inputs (Level 2) [Member] | Other [Member] | Other [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	710	897
Significant Unobservable Inputs (Level 3) [Member] | Investments in equity securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Investments in equity securities [Member] | U.S. Large Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Investments in equity securities [Member] | U.S. Mid Cap [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Investments in equity securities [Member] | International [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Investments in equity securities [Member] | Alternative Strategies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Debt securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Debt securities [Member] | Inflation Protected [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Debt securities [Member] | Fixed Income [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Debt securities [Member] | High Yield [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Other [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	710	897
Significant Unobservable Inputs (Level 3) [Member] | Other [Member] | Commodities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Other [Member] | Real Estate [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets
Significant Unobservable Inputs (Level 3) [Member] | Other [Member] | Guaranteed deposit [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets	710	897
Significant Unobservable Inputs (Level 3) [Member] | Other [Member] | Other [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total Pension Plan Assets