Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 500,062	$ 476,492
Accounts receivable:
Trade, net of allowance for uncollectible accounts of $7,525 and $4,735, respectively	120,659	104,724
Unbilled revenue	39,883	28,542
Costs in excess of billing	3,436	2,034
Current deferred tax assets	32,331	31,180
Other current assets	36,664	51,301
Total current assets	733,035	694,273
Property and equipment	2,474,882	2,241,444
Less accumulated depreciation	(554,909)	(506,060)
Property and equipment, net	1,919,973	1,735,384
Other assets:
Equity investments	145,588	149,623
Goodwill	62,294	62,146
Other assets, net	73,306	59,272
Total assets	2,934,196	2,700,698
Current liabilities:
Accounts payable	98,804	83,403
Accrued liabilities	66,788	104,923
Income tax payable	0	9,143
Current maturities of long-term debt	71,497	28,144
Total current liabilities	237,089	225,613
Long-term debt	722,515	523,228
Deferred tax liabilities	257,852	260,275
Other non-current liabilities	41,414	38,108
Total liabilities	$ 1,258,870	$ 1,047,224
Commitments and contingencies
Shareholders’ equity:
Common stock, no par, 240,000 shares authorized, 105,949 and 105,586 shares issued, respectively	$ 939,504	$ 934,447
Retained earnings	798,286	781,279
Accumulated other comprehensive loss	(62,464)	(62,252)
Total shareholders’ equity	1,675,326	1,653,474
Total liabilities and shareholders’ equity	$ 2,934,196	$ 2,700,698