Condensed Consolidating Statement of Earnings and Comprehensive Earnings (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Revenue	$ 284,713	$ 359,371	$ 376,315	$ 366,121	$ 278,663	$ 302,395	$ 332,658	$ 297,504	$ 1,386,520	$ 1,211,220	$ 1,143,492
Cost of Goods Sold									1,047,764	899,175	911,875
Gross Profit	61,377	94,566	96,754	86,059	61,500	87,380	91,210	71,955	338,756	312,045	231,617
Equity in Earnings of Unconsolidated Joint Venture									43,419	42,386	39,083
Corporate General and Administrative Expense									(41,205)	(33,940)	(37,193)
Legal Settlements									(45,098)
Other Non-Operating Income									3,728	2,139	2,328
Acquisition-Related Expense										(5,480)
Interest Expense, net									(27,638)	(22,631)	(16,583)
Earnings before Income Taxes	48,725	51,388	92,319	79,530	54,181	83,689	89,373	67,276	271,962	294,519	219,252
Income Taxes									(15,330)	(96,300)	(66,660)
Net Earnings	$ 37,008	$ 101,380	$ 63,362	$ 54,882	$ 36,251	$ 56,387	$ 60,237	$ 45,344	256,632	198,219	152,592
Net Actuarial Change in Benefit Plans, net of tax									3,384	4,013	658
Comprehensive Earnings									260,016	202,232	153,250
Eliminations [Member]
Equity in Earnings of Unconsolidated Joint Venture									(43,419)	(42,386)	(39,083)
Equity in Earnings of Subsidiaries									(289,950)	(210,923)	(160,018)
Earnings before Income Taxes									(333,369)	(253,309)	(199,101)
Net Earnings									(333,369)	(253,309)	(199,101)
Net Actuarial Change in Benefit Plans, net of tax									(3,384)	(4,013)	(658)
Comprehensive Earnings									(336,753)	(257,322)	(199,759)
Parent [Member]
Equity in Earnings of Unconsolidated Joint Venture									43,419	42,386	39,083
Equity in Earnings of Subsidiaries									289,950	210,923	160,018
Corporate General and Administrative Expense									(37,825)	(28,545)	(32,047)
Legal Settlements									(45,098)
Other Non-Operating Income									(233)	(534)	(398)
Acquisition-Related Expense										(5,480)
Interest Expense, net									(27,609)	(51,315)	(39,038)
Earnings before Income Taxes									222,604	167,435	127,618
Income Taxes									34,028	30,784	24,974
Net Earnings									256,632	198,219	152,592
Net Actuarial Change in Benefit Plans, net of tax									3,384	4,013	658
Comprehensive Earnings									260,016	202,232	153,250
Guarantor Subsidiaries [Member]
Revenue									1,386,520	1,211,220	1,143,492
Cost of Goods Sold									1,047,764	899,175	911,875
Gross Profit									338,756	312,045	231,617
Equity in Earnings of Unconsolidated Joint Venture									43,419	42,386	39,083
Corporate General and Administrative Expense									(3,380)	(5,395)	(5,146)
Other Non-Operating Income									3,961	2,673	2,726
Acquisition-Related Expense										0
Interest Expense, net									(29)	28,684	22,455
Earnings before Income Taxes									382,727	380,393	290,735
Income Taxes									(49,358)	(127,084)	(91,634)
Net Earnings									333,369	253,309	199,101
Net Actuarial Change in Benefit Plans, net of tax									3,384	4,013	658
Comprehensive Earnings									$ 336,753	$ 257,322	$ 199,759