Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 156,233	$ 119,028
Marketable securities	35	11,518
Accounts receivable, net of allowance for bad debts	247,028	405,370
Prepaid expenses and other current assets	102,111	119,479
Assets held for sale	400	14,200
Total current assets	505,807	669,595
Drilling and other property and equipment, net of accumulated depreciation	5,726,935	6,378,814
Other assets	139,135	101,485
Total assets	6,371,877	7,149,894
Current liabilities:
Accounts payable	30,242	70,272
Accrued liabilities	182,159	253,769
Taxes payable	23,898	15,093
Short-term borrowings	104,200	286,589
Total current liabilities	340,499	625,723
Long-term debt	1,980,884	1,979,778
Deferred tax liability	197,011	276,529
Other liabilities	103,349	155,094
Total liabilities	2,621,743	3,037,124
Commitments and contingencies (Note 12)
Stockholders' equity:
Preferred stock (par value $0.01, 25,000,000 shares authorized, none issued and outstanding)
Common stock (par value $0.01, 500,000,000 shares authorized; 143,997,757 shares issued and 137,169,663 shares outstanding at December 31, 2016; 143,978,877 shares issued and 137,158,706 shares outstanding at December 31, 2015)	1,440	1,440
Additional paid-in capital	2,004,514	1,999,634
Retained earnings	1,946,765	2,319,136
Accumulated other comprehensive gain (loss)	1	(5,035)
Treasury stock, at cost (6,828,094 and 6,820,171 shares of common stock at December 31, 2016 and 2015, respectively)	(202,586)	(202,405)
Total stockholders' equity	3,750,134	4,112,770
Total liabilities and stockholders' equity	$ 6,371,877	$ 7,149,894