Summary of Significant Accounting Policies - Computation of Basic EPS to Dilutive EPS (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net earnings	$ 53,470	$ 42,093	$ 90,701	$ 80,345
Effect of stock options and stock grants, Net Earnings	0	0	0	0
Net earnings per share, diluted, Net Earnings	$ 53,470	$ 42,093	$ 90,701	$ 80,345
Net earnings per share, basic, Weighted Average Shares	141,973,522	135,650,599	142,045,779	135,572,859
Effect of stock options and stock grants, Weighted Average Shares	480,561	567,636	473,529	622,952
Net earnings per share, diluted, Weighted Average Shares	142,454,083	136,218,235	142,519,308	136,195,811
Net earnings per share, basic, Per Share Amount	$ 0.38	$ 0.31	$ 0.64	$ 0.59
Effect of stock options and stock grants, Per Share Amount	0		0
Net earnings per share, diluted, Per Share Amount	$ 0.38	$ 0.31	$ 0.64	$ 0.59