CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities
Net earnings	$ 44,921,000	$ 40,158,000
Adjustments to reconcile net earnings to net cash provided by operating activities
Depreciation, depletion, accretion and amortization	71,563,000	69,406,000
Net gain on sale of property, plant & equipment and businesses	(369,000)	(555,000)
Contributions to pension plans	(2,374,000)	(2,343,000)
Share-based compensation expense	6,488,000	4,321,000
Deferred tax expense (benefit)	153,000	(17,879,000)
Changes in assets and liabilities before initial effects of business acquisitions and dispositions	(28,069,000)	(1,566,000)
Other, net	1,839,000	(2,814,000)
Net cash provided by operating activities	94,152,000	88,728,000
Investing Activities
Purchases of property, plant & equipment	(133,022,000)	(108,284,000)
Proceeds from sale of property, plant & equipment	1,239,000	1,086,000
Payment for businesses acquired, net of acquired cash	(185,067,000)	(1,611,000)
Decrease in restricted cash	9,033,000	1,150,000
Other, net	0	1,549,000
Net cash used for investing activities	(307,817,000)	(106,110,000)
Financing Activities
Payment of current maturities and long-term debt	(5,000)	(5,000)
Proceeds from issuance of long-term debt	350,000,000	0
Debt discounts and issuance costs	(4,565,000)	0
Purchases of common stock	(49,221,000)	(23,433,000)
Dividends paid	(33,152,000)	(26,718,000)
Share-based compensation, shares withheld for taxes	(21,424,000)	(24,636,000)
Other, net	3,000	0
Net cash provided by (used for) financing activities	241,636,000	(74,792,000)
Net increase (decrease) in cash and cash equivalents	27,971,000	(92,174,000)
Cash and cash equivalents at beginning of year	258,986,000	284,060,000
Cash and cash equivalents at end of period	$ 286,957,000	$ 191,886,000