Supplemental Cash Flow Disclosures - Non-Cash Investing and Financing Activities (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Supplemental Cash Flow [Line Items]
Capital property and equipment acquired on account, but not paid as of December 31	$ 6,192	$ 938	$ 1,064
Merger/acquisitions			300
Retirement Savings Plan		80	902
Dividend Reinvestment Plan			1,182
Conversion of debentures	186	181	202
Performance Incentive Plan	427	280	719
Director Stock Compensation Plan	$ 443	$ 456	$ 297