Company's pension plan weighted average (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Total pension plan sssets	100.00%	100.00%
Cash and certificates of deposit
Defined Benefit Plan Disclosure [Line Items]
Total pension plan sssets	11.10%	27.10%
Equity Securities:
Defined Benefit Plan Disclosure [Line Items]
Total pension plan sssets	58.50%	39.30%
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan sssets	30.40%	33.60%