Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 119,028	$ 233,623
Marketable securities	11,518	16,033
Accounts receivable, net of allowance for bad debts	405,370	463,862
Prepaid expenses and other current assets	119,479	185,541
Assets held for sale	14,200
Total current assets	669,595	899,059
Drilling and other property and equipment, net of accumulated depreciation	6,378,814	6,945,953
Other assets	116,480	176,277
Total assets	7,164,889	8,021,289
Current liabilities:
Accounts payable	70,272	138,444
Accrued liabilities	253,769	426,592
Taxes payable	15,093	41,648
Short-term borrowings	286,589
Current portion of long-term debt		249,962
Total current liabilities	625,723	856,646
Long-term debt	1,994,773	1,994,526
Deferred tax liability	276,529	530,394
Other liabilities	155,094	188,160
Total liabilities	$ 3,052,119	$ 3,569,726
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; 143,978,877 shares issued and 137,158,706 shares outstanding at December 31, 2015; 143,960,260 shares issued and 137,147,899 shares outstanding at December 31, 2014)	$ 1,440	$ 1,440
Additional paid-in capital	1,999,634	1,993,898
Retained earnings	2,319,136	2,661,999
Accumulated other comprehensive gain (loss)	(5,035)	(3,605)
Treasury stock, at cost (6,820,171 and 6,812,361 shares of common stock at December 31, 2015 and 2014, respectively)	(202,405)	(202,169)
Total stockholders' equity	4,112,770	4,451,563
Total liabilities and stockholders' equity	$ 7,164,889	$ 8,021,289