Quarterly Results (unaudited) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 223,780	$ 291,529	$ 284,808	$ 266,251	$ 189,894	$ 228,812	$ 252,646	$ 227,044	$ 1,066,368	$ 898,396	$ 642,562
Gross Profit	43,522	79,149	75,061	56,401	29,528	49,848	59,479	46,604	254,133	185,459	103,245
Earnings Before Income Taxes	44,698	77,866	74,577	55,786	29,767	48,833	58,688	44,516	252,927	181,804	84,096
Net Earnings	$ 46,794	$ 52,030	$ 50,319	$ 37,710	$ 22,618	$ 31,621	$ 39,903	$ 30,101	$ 186,853	$ 124,243	$ 57,744
Diluted Earnings Per Share	$ 0.93	$ 1.03	$ 1.00	$ 0.75	$ 0.45	$ 0.63	$ 0.80	$ 0.60	$ 3.71	$ 2.49	$ 1.22