Schedule of Basic Weighted Average Shares Reconciles to Diluted Weighted Average Shares Outstanding (Detail) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Weighted Average Number of Shares Outstanding [Line Items]
Basic weighted average common shares outstanding	81,829	83,180	82,013	82,987
Dilutive effect of stock options, unvested shares, performance share units, and DCUs	905	910	930	1,004
Diluted weighted average common shares outstanding	82,734	84,090	82,943	83,991