Unaudited Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income	$ 12,727	$ 11,155
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	30,195	29,879
(Gain) loss on sale of assets	126	(4,825)
Amortization of stock-based compensation	5,796	3,377
Amortization of deferred financing costs	819	2,076
Loss on extinguishment of debt		1,368
Provision for doubtful accounts receivable, net of write-offs	(425)	87
Deferred income tax provision	380	690
Foreign currency transaction gain	(146)	995
Change in operating assets and liabilities:
Accounts receivable	(33,689)	(2,523)
Prepaids and other	1,603	(3,411)
Accounts payable	(4,351)	2,345
Other accrued liabilities and other	(824)	2,764
Net cash provided by operating activities	12,211	43,977
Cash flows from investing activities:
Purchases of vessels, equipment and other fixed assets	(110,968)	(80,869)
Release of deposits held in escrow	14,771
Proceeds from disposition of vessels and equipment	648	23,475
Net cash used in investing activities	(95,549)	(57,394)
Cash flows from financing activities:
Cash dividends	(13,345)
Stock repurchases	(12,389)
Debt issuance costs	(1,579)	(9,036)
Proceeds from issuance of stock	683	406
Proceeds from issue of 6.375% Senior Notes		300,000
Repayment of 7.75% Senior Notes		(160,000)
Repayments of secured credit facility		(101,667)
Borrowings under revolving loan facility, net		974
Debt extinguishment cost		(2,274)
Proceeds from exercise of stock options		2,398
Net cash (used in) provided by financing activities	(26,630)	30,801
Effect of exchange rate changes on cash	(2,506)	262
Net increase (decrease) in cash and cash equivalents	(112,474)	17,646
Cash and cash equivalents at beginning of the period	185,175	128,817
Cash and cash equivalents at end of period	72,701	146,463
Supplemental cash flow information:
Interest paid, net of interest capitalized	10,272	8,544
Income taxes paid, net	$ 2,467	$ 2,962