Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 325,092	$ 266,592
Accounts receivable:
Trade, net of allowance for uncollectible accounts of $2,752	91,001	113,336
Unbilled and other	66,396	29,947
Other current assets	47,450	41,768
Total current assets	529,939	451,643
Property and equipment	2,727,760	2,695,772
Less accumulated depreciation	(956,209)	(889,783)
Property and equipment, net	1,771,551	1,805,989
Other assets, net	76,985	105,205
Total assets	2,378,475	2,362,837
Current liabilities:
Accounts payable	62,844	81,299
Accrued liabilities	84,431	71,680
Income tax payable	5,859	2,799
Current maturities of long-term debt	46,784	109,861
Total current liabilities	199,918	265,639
Long-term debt	401,265	385,766
Deferred tax liabilities	102,742	103,349
Other non-current liabilities	42,382	40,690
Total liabilities	746,307	795,444
Shareholders’ equity:
Common stock, no par, 240,000 shares authorized, 148,147 and 147,740 shares issued, respectively	1,306,703	1,284,274
Retained earnings	396,781	352,906
Accumulated other comprehensive loss	(71,316)	(69,787)
Total shareholders’ equity	1,632,168	1,567,393
Total liabilities and shareholders’ equity	$ 2,378,475	$ 2,362,837