Guarantor Subsidiaries - Schedule of Condensed Consolidating Statements of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Operating and other revenues	$ (453,017)	$ (252,839)	$ (178,819)
Operating expenses	(319,031)	(267,539)	(235,896)
General and administrative	(45,130)	(42,476)	(42,169)
Merger transaction expense	7,991	8,749	0
Interest expense	(52,703)	(57,710)	(59,373)
Interest income and other income (expense)	94,885	(15,992)	(11,759)
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	123,047	(139,627)	(170,378)
(Provision for) Benefit from income taxes	(1,827)	1,402	0
Equity in earnings (loss) of subsidiaries	0	0	0
Net income (loss)	121,220	(138,225)	(170,378)
Reportable Legal Entities [Member] | Parent Guarantor
Condensed Financial Statements, Captions [Line Items]
Operating and other revenues	0
Operating expenses	0
General and administrative	0
Merger transaction expense	0
Interest expense	0
Interest income and other income (expense)	0
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	0
(Provision for) Benefit from income taxes	0
Equity in earnings (loss) of subsidiaries	121,220
Net income (loss)	121,220
Reportable Legal Entities [Member] | Subsidiary Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Operating and other revenues	(453,017)
Operating expenses	(319,031)
General and administrative	(45,130)
Merger transaction expense	7,991
Interest expense	(52,703)
Interest income and other income (expense)	94,885
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	123,047
(Provision for) Benefit from income taxes	(1,827)
Equity in earnings (loss) of subsidiaries	0
Net income (loss)	121,220
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Operating and other revenues		(582)	(628)
Operating expenses		(1,420)	(715)
General and administrative		0	0
Merger transaction expense		0
Interest expense		0	0
Interest income and other income (expense)		0	0
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries		(838)	(87)
(Provision for) Benefit from income taxes		0	0
Equity in earnings (loss) of subsidiaries		0	0
Net income (loss)		(838)	(87)
Reportable Legal Entities [Member] | Parent Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Operating and other revenues		(252,257)	(178,191)
Operating expenses		(266,119)	(235,181)
General and administrative		(42,476)	(42,169)
Merger transaction expense		8,749
Interest expense		(57,710)	(59,373)
Interest income and other income (expense)		(15,992)	(11,759)
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries		(138,789)	(170,291)
(Provision for) Benefit from income taxes		1,402	0
Equity in earnings (loss) of subsidiaries		(838)	(87)
Net income (loss)		(138,225)	(170,378)
Intercompany Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Operating and other revenues	0	0	0
Operating expenses	0	0	0
General and administrative	0	0	0
Merger transaction expense	0	0
Interest expense	0	0	0
Interest income and other income (expense)	0	0	0
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries	0	0	0
(Provision for) Benefit from income taxes	0	0	0
Equity in earnings (loss) of subsidiaries	(121,220)	838	87
Net income (loss)	$ (121,220)	$ 838	$ 87