Reconciliation of Basic and Diluted Weighted-average Shares Outstanding (Detail)	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Weighted Average Number of Shares Outstanding [Line Items]
Basic weighted average shares outstanding	96,896,301		111,010,134		98,482,330		113,897,688
Weighted average dilutive options outstanding	929,700		1,821,074		1,200,550		1,824,323
Diluted weighted average shares outstanding	97,826,001		112,831,208		99,682,880		115,722,011
Antidilutive shares	160,000	[1]	1,075,248	[1]	113,407	[1]	1,144,232	[1]

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