Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 476,492	$ 478,200
Accounts receivable:
Trade, net of allowance for uncollectible accounts of $4,735 and $2,234, respectively	104,724	156,925
Unbilled revenue	28,542	25,732
Costs in excess of billing	2,034	1,508
Current deferred tax assets	31,180	51,573
Other current assets	51,301	29,709
Total current assets	694,273	743,647
Property and equipment	2,241,444	1,963,706
Less accumulated depreciation	(506,060)	(431,489)
Property and equipment, net	1,735,384	1,532,217
Other assets:
Equity investments	149,623	157,919
Goodwill	62,146	63,230
Other assets, net	59,272	47,267
Total assets	2,700,698	2,544,280
Current liabilities:
Accounts payable	83,403	72,602
Accrued liabilities	104,923	96,482
Income tax payable	9,143	760
Current maturities of long-term debt	28,144	20,376
Total current liabilities	225,613	190,220
Long-term debt	523,228	545,776
Deferred tax liabilities	260,275	265,879
Other non-current liabilities	38,108	18,295
Total liabilities	1,047,224	1,020,170
Commitments and contingencies
Shareholders' equity:
Common stock, no par, 240,000 shares authorized, 105,586 and 105,640 shares issued, respectively	934,447	933,507
Retained earnings	781,279	586,232
Accumulated other comprehensive loss	(62,252)	(20,688)
Total controlling interest shareholders' equity	1,653,474	1,499,051
Noncontrolling interests		25,059
Total equity	1,653,474	1,524,110
Total liabilities and shareholders' equity	$ 2,700,698	$ 2,544,280