CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Class A [Member]	Common Class B [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]
Opening Balance SHARES at Dec. 31, 2016		33,510,184	7,197,532
Conversion of Class B common stock to Class A common stock SHARES		3,152,333	(3,152,333)
Compensation expense related to granting of restricted stock awards SHARES		2,066,241	0
Issuance of common stock related to an incentive plan SHARES		14,833	0
Common stock repurchase SHARES		(932,600)	0
Equity Awards assumed in Merger		618,325	0
Stock options assumed in Merger		0	0
Exercise of stock options SHARES		8,250	0
Shares Issued Pursuant to Acquisition		101,407,494	0
Purchase of vested employee restricted stock units SHARES		(169,279)	0
Ending Balance SHARES at Dec. 31, 2017		139,675,781	4,045,199
Opening Balance VALUE at Dec. 31, 2016	$ 393,374	$ 335	$ 72	$ 605,603	$ (212,636)
NET INCOME (LOSS)	233,849	0	0	0	233,849
Conversion of Class B common stock to Class A common stock VALUE	0	32	(32)	0	0
Compensation expense related to granting of restricted stock awards VALUE	9,567	21	0	9,546	0
Issuance of common stock related to an incentive plan VALUE	182	0	0	182	0
Common stock repurchase VALUE	(10,675)	(9)	0	(10,666)	0
Purchase of vested employee restricted stock units	(2,565)	(2)	0	(2,563)	0
Payments of dividends VALUE	(29,296)	0	0	(29,296)	0
Exercise of stock options VALUE	42	0	0	42	0
Preferred stock dividend	(2,574)	0	0	(2,574)	0
Dividend equivalents, net of forfeitures	(1,556)	0	0	(1,556)	0
Stock Issued in Acquisition - VALUE	1,161,116	1,014	0	1,160,102	0
Equity awards assumed in Merger VALUE	6,777	6	0	6,771	0
Stock options assumed in Merger VALUE	1,007	0	0	1,007	0
Ending Balance VALUE at Dec. 31, 2017	$ 1,764,360	$ 1,397	$ 40	1,737,132	25,791
Compensation expense related to granting of stock options SHARES	0
Compensation expense related to granting of restricted stock awards SHARES		1,041,054	0
Issuance of common stock related to an incentive plan SHARES		99,582	0
Common stock repurchase SHARES		(1,833,200)	0
Exercise of stock options SHARES	48,500	48,500	0
Purchase of vested employee restricted stock units SHARES		(504,471)	0
Ending Balance SHARES at Jun. 30, 2018		138,527,246	4,045,199
NET INCOME (LOSS)	$ (11,437)	$ 0	$ 0	0	(11,437)
Compensation expense related to granting of restricted stock awards VALUE	7,653	10	0	7,643	0
Issuance of common stock related to an incentive plan VALUE	709	1	0	708	0
Common stock repurchase VALUE	(19,379)	(18)	0	(19,361)	0
Purchase of vested employee restricted stock units	(5,172)	(5)	0	(5,167)	0
Payments of dividends VALUE	(25,782)	0	0	(25,782)	0
Exercise of stock options VALUE	65	0	0	65	0
Dividend equivalents, net of forfeitures	469	0	0	469	0
Ending Balance VALUE at Jun. 30, 2018	$ 1,711,486	$ 1,385	$ 40	$ 1,695,707	$ 14,354