CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 498,003	$ 449,511
Marketable securities, short-term	164,740	272,031
Accounts receivable, net of allowance for doubtful accounts of $2,735 and $5,814, respectively	361,459	324,189
Inventories	35,866	31,688
Prepaid expenses and other current assets	108,708	80,948
Total current assets	1,168,776	1,158,367
Marketable securities, long-term	10,212	39,948
Property, plant and equipment, net	400,528	348,793
Equity method investments	52,829	54,606
Goodwill and intangible assets, net	87,629	89,068
Deferred tax assets	45,524	49,334
Other assets	17,233	43,893
Total assets	1,782,731	1,784,009
Current liabilities:
Accounts payable	41,881	36,776
Accrued liabilities	180,093	195,562
Deferred revenues	296,011	267,713
Total current liabilities	517,985	500,051
Income tax payable	119,349	114,091
Other long-term liabilities	17,937	15,579
Total liabilities	655,271	629,721
Commitments and contingencies (Notes 8 and 9)
Stockholders' equity:
Preferred stock, $0.0001 par value (5,000 shares authorized; none issued)	0	0
Common stock, $0.0001 par value (200,000 shares authorized; 80,144 and 80,040 issued and outstanding, respectively)	8	8
Additional paid-in capital	858,632	886,435
Accumulated other comprehensive income (loss), net	1,484	571
Retained earnings	267,336	267,274
Total stockholders’ equity	1,127,460	1,154,288
Total liabilities and stockholders’ equity	$ 1,782,731	$ 1,784,009