Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current Assets:
Cash	$ 2,849	$ 5,091
Short-term investments	50,601	100,027
Accounts receivable - net
Trade	137,179	98,338
Other	3,974	958
Inventories of spare parts - net	66,074	57,243
Prepaid expenses	10,137	7,169
Work in progress	77,764
Other current assets	988
Deferred income taxes	11,967	8,133
Income taxes receivable	1,613	346
Total current assets	363,146	277,305
Property and equipment - net	749,501	659,756
Restricted investments	14,685
Other	20,562	27,071
Total assets	1,147,894	964,132
Current Liabilities:
Accounts payable	26,308	17,697
Accrued and other current liabilities	117,162	29,051
Total current liabilities	143,470	46,748
Long-term debt	386,755	346,047
Deferred income taxes	105,418	85,937
Other long-term liabilities	12,636	8,063
Commitments and contingencies (Note 12)
Shareholders' Equity:
Additional paid-in capital	295,582	291,403
Accumulated other comprehensive loss	(51)	(93)
Retained earnings	202,553	184,496
Total shareholders' equity	499,615	477,337
Total liabilities and shareholders' equity	1,147,894	964,132
Voting Common Stock
Shareholders' Equity:
Common stock	285	285
Total shareholders' equity	285	285
Non-Voting Common Stock
Shareholders' Equity:
Common stock	1,246	1,246
Total shareholders' equity	$ 1,246	$ 1,246