Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 222,151	$ 128,817
Trade accounts receivable, net of allowance for doubtful accounts of $223 and $198, respectively	85,352	85,214
Other accounts receivable	8,090	6,314
Prepaid expenses and other current assets	25,260	21,197
Total current assets	340,853	241,542
Vessels, equipment, and other fixed assets at cost, net of accumulated depreciation of $350,081 and $329,299, respectively	1,163,754	1,143,441
Construction in progress	49,392	37,107
Goodwill	32,713	31,153
Intangibles, net of accumulated amortization of $10,751 and $10,030, respectively	23,848	24,569
Deferred costs and other assets	29,023	21,987
Total assets	1,639,583	1,499,799
Current liabilities:
Current portion of long-term debt	79,663	1,667
Accounts payable	20,275	14,475
Income and other taxes payable	6,029	5,568
Accrued personnel costs	21,319	23,059
Accrued interest expense	2,396	5,777
Fair value of derivative	2,805	3,530
Other accrued liabilities	8,489	8,565
Total current liabilities	140,976	62,641
Long-term debt	347,028	305,830
Long-term income taxes:
Deferred tax liabilities	106,311	105,131
Other income taxes payable	20,992	22,769
Other liabilities	6,622	6,568
Stockholders' equity:
Preferred stock, no par value; 2,000 authorized; no shares issued
Class A Common stock, $0.01 par value; 60,000 shares authorized; 26,803 and 26,631 shares issued and 26,803 and 26,617 shares outstanding, respectively; Class B Common Stock $0.01 par value; 60,000 shares authorized; no shares issued	265	262
Additional paid-in capital	382,196	379,673
Retained earnings	583,493	586,402
Accumulated other comprehensive income	51,700	31,105
Treasury stock, at cost	(9,114)	(8,968)
Deferred compensation expense	9,114	8,386
Total stockholders' equity	1,017,654	996,860
Total liabilities and stockholders' equity	$ 1,639,583	$ 1,499,799