Schedule of Basic Weighted Average Shares Reconciles to Diluted Weighted Average Shares (Detail) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic weighted average common shares outstanding	83,180	82,151	82,987	81,790
Dilutive effect of stock options, unvested shares, and DCUs	910	1,627	1,004	1,717
Diluted weighted average common shares outstanding	84,090	83,778	83,991	83,507