Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 606,166	$ 1,412,517
Short-term investments	4,540	28,271
Accounts receivable, net of allowance for doubtful accounts of $15,950 and $18,228	630,119	576,313
Other current assets	274,857	232,027
Total current assets	1,515,682	2,249,128
Long-term investments	0	9,243
Property, plant and equipment, net	11,026,020	9,394,602
Goodwill	4,836,388	4,411,762
Intangible assets, net	2,333,296	2,384,972
Other assets	533,252	241,750
Total assets	20,244,638	18,691,457
Current liabilities:
Accounts payable and accrued expenses	756,692	719,257
Accrued property, plant and equipment	179,412	220,367
Current portion of capital lease and other financing obligations	77,844	78,705
Current portion of mortgage and loans payable	73,129	64,491
Current portion of senior notes	300,999	0
Other current liabilities	126,995	159,914
Total current liabilities	1,515,071	1,242,734
Capital lease and other financing obligations, less current portion	1,441,077	1,620,256
Mortgage and loans payable, less current portion	1,310,663	1,393,118
Senior notes, less current portion	8,128,785	6,923,849
Other liabilities	629,763	661,710
Total liabilities	13,025,359	11,841,667
Stockholders' equity:
Preferred stock, $0.001 par value per share: 100,000,000 shares authorized in 2018 and 2017; zero shares issued and outstanding	0	0
Common stock, $0.001 par value per share: 300,000,000 shares authorized in 2018 and 2017; 81,119,117 issued and 80,722,258 outstanding in 2018 and 79,440,404 issued and 79,038,062 outstanding in 2017	81	79
Additional paid-in capital	10,751,313	10,121,323
Treasury stock, at cost; 396,859 shares in 2018 and 402,342 shares in 2017	(145,161)	(146,320)
Accumulated dividends	(3,331,200)	(2,592,792)
Accumulated other comprehensive loss	(945,702)	(785,189)
Retained earnings	889,948	252,689
Total stockholders' equity	7,219,279	6,849,790
Total liabilities and stockholders' equity	$ 20,244,638	$ 18,691,457