Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Condensed Consolidated Statements of Cash Flows
Net cash provided by Operating Activities	$ 207,475	$ 249,394
Cash flows from Investing Activities:
Additions to property and equipment, including pre-delivery payments, net	(232,717)	(215,950)
Net cash used in investing activities	(232,717)	(215,950)
Cash flows from Financing Activities:
Proceeds from exercise of stock options	2,376	1,263
Long-term borrowings	132,000	133,000
Repayments of long-term debt and capital lease obligations	(45,200)	(35,219)
Debt issuance costs	(12,416)	(3,118)
Change in restricted cash	(16,000)
Net cash provided by financing activities	60,760	95,926
Net increase in cash and cash equivalents	35,518	129,370
Cash and cash equivalents - Beginning of Period	405,880	304,115
Cash and cash equivalents - End of Period	$ 441,398	$ 433,485