CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net earnings (loss)	$ (346,963)	$ 44,457
Adjustments to reconcile net earnings (loss) to net cash provided by operations:
Depreciation and amortization	55,786	55,223
Provision (benefit) for deferred income taxes	(35,242)	12,490
Impairments and other charges	561,274	0
Amortization of unearned share-based compensation	5,331	4,900
Amortization of major maintenance costs	7,103	4,974
Other	112	(1,778)
Decrease in cash flows resulting from changes in operating assets and liabilities, net	(175,900)	(81,737)
Net cash provided by operating activities	71,501	38,529
Cash flows from investing activities:
Capital expenditures	(49,225)	(60,932)
Acquisitions of businesses and marine equipment	(60,422)	(247,470)
Proceeds from disposition of assets	3,993	13,187
Net cash used in investing activities	(105,654)	(295,215)
Cash flows from financing activities:
Borrowings (payments) on bank credit facilities, net	485,001	(240,801)
Borrowings on long-term debt	0	500,000
Payments on long-term debt	(150,000)	0
Payments of debt issue costs	0	(2,232)
Proceeds from exercise of stock options	353	1,415
Payments related to tax withholding for share-based compensation	(3,165)	(2,003)
Other	(202)	(204)
Net cash provided by (used in) financing activities	331,987	256,175
Increase (decrease) in cash and cash equivalents	297,834	(511)
Cash and cash equivalents, beginning of year	24,737	7,800
Cash and cash equivalents, end of period	322,571	7,289
Cash paid (received) during the period:
Interest paid	21,734	23,257
Income taxes refunded	(160)	(1,024)
Operating cash outflow from operating leases	9,738	10,142
Non-cash investing activity:
Capital expenditures included in accounts payable	(2,707)	(5,022)
Right-of-use assets obtained in exchange for lease obligations	$ 4,677	$ 1,292