Schedule of Basic Weighted Average Shares Reconciles to Diluted Weighted Average Shares Outstanding (Detail) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accounting Policies [Abstract]
Basic weighted average common shares outstanding (in shares)	81,259	82,482	81,762	82,820
Dilutive effect of stock options, unvested shares, and DCUs (in shares)	959	888	939	965
Diluted weighted average common shares outstanding (in shares)	82,218	83,370	82,701	83,785