Supplemental Balance Sheet and Income Statement Information - Reclass Accumulated Other (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Unrealized (gains) losses on available-for-sale securities that were reclassified from net income
Impairments and other charges	$ 102,570	$ 69,620	$ 99,903	$ 76,664
Interest expense	51,491	60,592	103,843	121,978
General and administrative expenses	64,415	67,823	132,582	142,394
Income (loss) from continuing operations before income taxes	(181,403)	(171,937)	(254,980)	(291,979)
Income tax expense (benefit)	11,398	23,278	41,197	46,823
Net income (loss)	(192,835)	(195,799)	(296,368)	(339,461)
Reclassification adjustment for (gains)/losses included in net income (loss)
Unrealized (gains) losses on available-for-sale securities that were reclassified from net income
Interest expense	142	142	282	282
General and administrative expenses	54	54	108	108
Income (loss) from continuing operations before income taxes	(196)	(196)	(390)	(390)
Income tax expense (benefit)	(48)	(48)	(94)	(91)
Net income (loss)	$ (148)	$ (148)	$ (296)	$ (299)