Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Adjustment of Warrants	$ (21,400)	$ 17,900	$ 11,700	$ (900)	$ 20,400	$ (34,400)	$ (67,600)	$ 1,900	$ 7,400	$ (81,800)
Deferred Federal Income Tax Expense (Benefit)									15,642	27,625	$ 11,338
REVENUES	280,779	204,919	203,607	203,040	322,971	254,101	253,211	237,917	892,345	1,068,200	768,870
Income (Loss) from Continuing Operations before Interest Expense, Interest Income, Income Taxes, Extraordinary Items, Noncontrolling Interests, Net	32,650	26,827	23,898	27,643	33,893	24,452	23,125	17,930
Net earnings (loss) from continuing operations	(5,196)	32,933	24,464	15,682	94,091	(28,229)	(53,918)	9,796	67,883	21,740	21,060
EARNINGS (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAXES	$ 866	$ 170	$ 170	$ 196	$ 1,026	$ (4,655)	$ 192	$ 192	$ 1,402	$ (3,245)	$ 2,428
Weighted average shares:
Basic (in shares)	58,740	58,739	58,739	58,840	58,733	58,733	59,035	59,133	58,765	58,907	61,330
Diluted (in shares)	58,740	68,323	68,363	59,558	68,987	58,733	59,035	64,949	68,356	59,686	62,994
Earnings (loss) per share from continuing operations
Basic (in dollars per share)	$ (0.09)	$ 0.56	$ 0.42	$ 0.27	$ 1.60	$ (0.48)	$ (0.91)	$ 0.17	$ 1.16	$ 0.37	$ 0.34
Diluted (in dollars per share)	$ (0.09)	$ 0.24	$ 0.21	$ 0.26	$ 1.11	$ (0.48)	$ (0.91)	$ 0.13	$ 0.89	$ 0.36	$ 0.33
Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement									$ 0	$ (12,923)	$ 0
Pension Plans [Member] | Continuing Operations [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement										5,300
Pension Plans [Member] | Discontinued Operations [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement										7,600
ACMI Services [Member]
REVENUES									548,839	614,741	492,859
2017 Tax Cuts and Jobs Act [Member]
Deferred Federal Income Tax Expense (Benefit)					$ 59,900				$ 0	$ (59,944)	$ 0