CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net earnings	$ 61,459	$ 53,617
Adjustments to reconcile net earnings to net cash provided by operations:
Depreciation and amortization	109,710	96,463
Provision for deferred income taxes	23,381	18,651
Amortization of unearned share-based compensation	13,551	5,924
Amortization of major maintenance costs	10,338	9,938
Amortization of debt issuance costs	578	588
Other	(1,778)	29
Increase (decrease) in cash flows resulting from changes in operating assets and liabilities, net	(63,484)	8,585
Net cash provided by operating activities	153,755	193,795
Cash flows from investing activities:
Capital expenditures	(152,911)	(92,509)
Acquisitions of businesses and marine equipment, net of cash acquired	(499,227)	0
Proceeds from disposition of assets	25,208	27,966
Net cash used in investing activities	(626,930)	(64,543)
Cash flows from financing activities:
Payments on bank credit facilities	(45,485)	(131,855)
Borrowings on long-term debt	499,295	0
Payment of debt issue costs	(4,263)	0
Proceeds from exercise of stock options	12,987	1,838
Payments related to tax withholding for share-based compensation	(4,813)	(2,874)
Other	(450)	(418)
Net cash provided by (used in) financing activities	457,271	(133,309)
Decrease in cash and cash equivalents	(15,904)	(4,057)
Cash and cash equivalents, beginning of year	20,102	5,634
Cash and cash equivalents, end of period	4,198	1,577
Cash paid during the period:
Interest paid	14,085	9,724
Income taxes paid (refunded)	(132)	16,274
Capital expenditures included in accounts payable	(16,498)	6,289
Non-cash investing activity:
Cash acquired in acquisition	$ 2,313	$ 0