Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018		Dec. 31, 2017
Stockholders' equity
Preferred stock, par value	$ 0.001		$ 0.001
Preferred stock, shares authorized	25,000,000		25,000,000
Preferred stock, shares issued	0		0
Preferred stock, shares outstanding	0		0
Common stock, par value	$ 0.001		$ 0.001
Common stock, shares authorized	600,000,000		600,000,000
Common stock, shares issued	462,355,725		402,549,346
Treasury stock, shares	1,941,749		457,041
Debt Instrument [Line Items]
Future interest payable - current	$ 105,125	[1]	$ 105,188
Future interest payable - long-term	2,664,211		2,979,086
Future interest payable on senior secured and convertible senior notes
Debt Instrument [Line Items]
Future interest payable - current	85,303		75,347
Future interest payable - long-term	$ 164,914		$ 241,472

[1] Future interest payable represents most of the interest due over the term of our 9% Senior Secured Second Lien Notes due 2021 (the “2021 Senior Secured Notes”), 9¼% Senior Secured Second Lien Notes due 2022 (the “2022 Senior Secured Notes”) and to a small extent our previously outstanding 3½% Convertible Senior Notes due 2024 (the “2024 Convertible Senior Notes”) and has been accounted for as debt in accordance with FASC 470-60, Troubled Debt Restructuring by Debtors. Our current maturities of long-term debt as of December 31, 2018 include $85.3 million of future interest payable related to the 2021 Senior Secured Notes and 2022 Senior Secured Notes that is due within the next twelve months. See January 2018 Senior Subordinated Note Exchanges and 2017 Senior Subordinated Note Exchanges below for further discussion.