Stock-Based Compensation Plans - Summary of Activity Related to Company's Restricted Stock (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total value of the restricted share grants	$ 2,657	$ 2,012	$ 2,002