CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) (USD $)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net earnings	$ 121,344,000	$ 100,314,000
Adjustments to reconcile net earnings to net cash provided by operations:
Depreciation and amortization	81,267,000	71,671,000
Provision for deferred income taxes	47,883,000	33,774,000
Amortization of unearned share-based compensation	5,061,000	4,489,000
Other	3,475,000	2,127,000
Decrease in cash flows resulting from changes in operating assets and liabilities, net	10,245,000	(75,773,000)
Net cash provided by operating activities	269,275,000	136,602,000
Cash flows from investing activities:
Capital expenditures	(168,175,000)	(153,846,000)
Acquisition of businesses and marine equipment	(3,643,000)	0
Proceeds from disposition of assets	13,111,000	6,651,000
Net cash used in investing activities	(158,707,000)	(147,195,000)
Cash flows from financing activities:
Payments on bank credit facilities, net	(112,870,000)	10,530,000
Borrowings on long-term debt	225,000,000	0
Payments on long-term debt	(226,000,000)	(13,003,000)
Proceeds from exercise of stock options	2,573,000	1,250,000
Payment of contingent liability	(5,000,000)	0
Excess tax benefit from equity compensation plans	2,253,000	2,375,000
Other	(2,320,000)	(1,003,000)
Net cash used in financing activities	(116,364,000)	149,000
Decrease in cash and cash equivalents	(5,796,000)	(10,444,000)
Cash and cash equivalents, beginning of year	11,059,000	16,249,000
Cash and cash equivalents, end of period	5,263,000	5,805,000
Cash paid (received) during the period:
Interest	8,012,000	10,619,000
Income taxes	$ 17,969,000	$ 19,174,000