Reconciliation of Basic and Diluted Weighted-average Shares Outstanding (Detail)	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Weighted Average Number of Shares Outstanding [Line Items]
Basic weighted average shares outstanding	95,125,843		104,779,422		97,355,334		110,603,070
Weighted average dilutive options outstanding	1,216,279		532,720		1,282,764		1,669,249
Diluted weighted average shares outstanding	96,342,122		105,312,142		98,638,098		112,272,319
Antidilutive shares	0	[1]	3,984,927	[1]	0	[1]	3,326,037	[1]

[1] Antidilutive shares are excluded from the calculation of diluted earnings per share.