CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net earnings	$ 32,666	$ 27,645
Adjustments to reconcile net earnings to net cash provided by operations:
Depreciation and amortization	54,218	48,170
Provision (benefit) for deferred income taxes	8,846	8,562
Amortization of unearned share-based compensation	7,551	2,693
Amortization of major maintenance costs	4,893	5,034
Amortization of debt issuance costs	259	200
Other	(1,773)	1,038
Decrease in cash flows resulting from changes in operating assets and liabilities, net	(87,926)	(8,140)
Net cash provided by operating activities	18,734	85,202
Cash flows from investing activities:
Capital expenditures	(40,961)	(45,765)
Acquisitions of businesses and marine equipment, net of cash acquired	(429,977)	0
Proceeds from disposition of assets	12,181	7,958
Net cash used in investing activities	(458,757)	(37,807)
Cash flows from financing activities:
Payments on bank credit facilities	(64,414)	(48,451)
Borrowings on long-term debt	499,295	0
Payment of debt issuance cost	(4,251)	0
Proceeds from exercise of stock options	292	1,258
Payments related to tax withholding for share-based compensation	(3,766)	(2,873)
Other	(225)	(207)
Net cash provided by (used in) financing activities	426,931	(50,273)
Decrease in cash and cash equivalents	(13,092)	(2,878)
Cash and cash equivalents, beginning of year	20,102	5,634
Cash and cash equivalents, end of period	7,010	2,756
Cash paid during the period:
Interest paid	10,763	8,856
Income taxes paid (refunded)	(721)	1,686
Capital expenditures included in accounts payable	(5,448)	(1,778)
Non-cash investing activity:
Cash acquired in acquisition	$ 2,313	$ 0