Changes in Issued and Outstanding Common Shares (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Beginning balance	14,198,000	14,047,000	13,956,000
Vested stock grants	59,000	50,000	60,000
Employee stock purchase plan	19,386	17,000	16,000
Stock options exercised	5,250	83,500	15,000
Treasury shares purchased	0	0	0
Ending balance	14,281,000	14,198,000	14,047,000