Summary of Share Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Number of Common Shares
Balance at January 1, 2013	440,453
Granted	20,229
Exercised	(10,964)	(3,906)	(2,037)
Forfeited or expired	(141,917)
Balance at December 31, 2013	307,801	440,453
Exercisable at December 31, 2013	263,657
Weighted Average Exercise Share Price
Balance at January 1, 2013	$ 29.17
Granted	$ 20.26
Exercised	$ 12.70
Forfeited or expired	$ 37.72
Balance at December 31, 2013	$ 25.23	$ 29.17
Exercisable at December 31, 2013	$ 26.19
Weighted average fair value of options granted during the year	$ 7.99	$ 7.85	$ 7.76
Weighted Average Contractual Remaining Life(Years)
Balance at end of period	2 years 4 months 24 days
Exercisable at end of period	1 year 10 months 24 days
Aggregate Intrinsic Value
Balance at January 1, 2013	$ 557
Granted	160
Exercised	118
Forfeited or expired	13
Balance at December 31, 2013	1,768	557
Exercisable at December 31, 2013	$ 1,384