Statement of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock Class A common stock	Common Stock Class B common stock	Treasury Stock Class A common stock	Additional Paid-in-Capital	Retained Earnings	Non-controlling Interest	Class A common stock	Total
Balance at Dec. 31, 2016	$ 57	$ 30	$ (358)	$ 447,137	$ (8,652)	$ 453,237		$ 891,451
Balance (in shares) at Dec. 31, 2016	57,025	29,832	23
Increase (Decrease) Stockholders' Equity
Net income (loss)					(83,603)	(53,890)		(137,493)
Balance at Jun. 30, 2017					(114,454)	398,662		761,337
Balance at Dec. 31, 2016	$ 57	$ 30	$ (358)	447,137	(8,652)	453,237		891,451
Balance (in shares) at Dec. 31, 2016	57,025	29,832	23
Increase (Decrease) Stockholders' Equity
Cumulative effect of adoption of ASU 2016-09				706	(706)
Stock-compensation expense	$ 1			5,239				5,240
Stock-compensation expense (in shares)	759
Cash tax distribution						(562)		(562)
Sale of common stock	$ 3			8,329				8,332
Sale of common stock (in shares)	3,716						3,700
Stock dividends on common stock	$ 5			17,495	(17,500)
Stock dividends on common stock (in shares)	5,000
Exchange of Class B Shares for Class A Shares	$ 6	$ (6)		53,441		(81,732)		(28,291)
Exchange of Class B shares for Class A shares (in shares)	6,113	(6,113)
Dividends and accretion on preferred stock	$ 2			2,152	(5,959)			(3,805)
Dividends and accretion on preferred stock (in shares)	1,740
Net income (loss)					(148,409)	(72,047)		(220,456)
Balance at Sep. 30, 2017	$ 74	$ 24	$ (358)	534,499	(181,226)	298,896		651,909
Balance (in shares) at Sep. 30, 2017	74,353	23,719	23
Balance at Jun. 30, 2017					(114,454)	398,662		761,337
Increase (Decrease) Stockholders' Equity
Sale of common stock (in shares)							0
Net income (loss)								(82,963)
Balance at Sep. 30, 2017	$ 74	$ 24	$ (358)	$ 534,499	$ (181,226)	$ 298,896		$ 651,909
Balance (in shares) at Sep. 30, 2017	74,353	23,719	23