CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash Flows From Operating Activities:
Net income (loss)	$ 177,636	$ 203,808
Adjustments to reconcile net income (loss) to net cash flows from operating activities:
Depreciation and amortization	155,115	178,519
Realized and unrealized losses (gains) on investments	(2,331)	36,727
Non-cash, stock-based compensation	11,003	9,041
Deferred tax expense (benefit)	(23,218)	(17,710)
Other, net	(8,546)	(32,404)
Changes in current assets and current liabilities, net	86,390	1,548
Net cash flows from operating activities	396,049	379,529
Cash Flows From Investing Activities:
(Purchases) Sales and maturities of marketable investment securities, net	(33,401)	59,465
Purchases of property and equipment	(93,803)	(66,715)
Other, net	9,425	3,207
Net cash flows from investing activities	(117,779)	(4,043)
Cash Flows From Financing Activities:
Redemption and repurchases of senior notes	(22,365)	(56,473)
Repayment of long-term debt and finance lease obligations	(6,232)	(9,630)
Other, net	(400)	(159)
Net cash flows from financing activities	(28,997)	(66,262)
Net increase (decrease) in cash, cash equivalents, restricted cash and cash equivalents	249,273	309,224
Cash, cash equivalents, restricted cash and cash equivalents, beginning of period (Note 4)	130,076	365,066
Cash, cash equivalents, restricted cash and cash equivalents, end of period (Note 4)	$ 379,349	$ 674,290