Earnings Per Share - Reconciliation of Average Share Amounts used to Compute Both Basic and Diluted Earnings Per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Weighted average shares outstanding:
Basic weighted average shares outstanding	117,922	114,484	117,035	114,603
Add: Dilutive effect of stock options	1,382	1,944	1,463	2,079
Diluted weighted average shares outstanding	119,304	116,428	118,498	116,682