Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Adjustment of Warrants	$ (72,900)	$ 92,000	$ (35,900)	$ 4,500	$ (21,400)	$ 17,900	$ 11,700	$ (900)	$ (2,300)	$ 7,400	$ (81,800)
Deferred Federal Income Tax Expense (Benefit)									14,155	15,642	27,625
REVENUES	403,351	366,073	334,576	348,183	280,779	204,919	203,607	203,040	1,452,183	892,345	1,068,200
Income (Loss) from Continuing Operations before Interest Expense, Interest Income, Income Taxes, Extraordinary Items, Noncontrolling Interests, Net	52,221	40,766	37,482	46,528	32,650	26,827	23,898	27,643
Net earnings from continuing operations	(41,104)	105,085	(26,632)	22,634	(5,196)	32,933	24,464	15,682	59,983	67,883	21,740
EARNINGS (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAXES	$ 914	$ 243	$ 31	$ 31	$ 866	$ 170	$ 170	$ 196	$ 1,219	$ 1,402	$ (3,245)
Weighted average shares:
Basic (in shares)	58,929	58,919	58,909	58,838	58,740	58,739	58,739	58,840	58,899	58,765	58,907
Diluted (in shares)	58,929	68,718	58,909	60,437	58,740	68,323	68,363	59,558	69,348	68,356	59,686
Earnings (loss) per share from continuing operations
Basic (in dollars per share)	$ (0.70)	$ 1.78	$ (0.45)	$ 0.38	$ (0.09)	$ 0.56	$ 0.42	$ 0.27	$ 1.02	$ 1.16	$ 0.37
Diluted (in dollars per share)	$ (0.70)	$ 0.19	$ (0.45)	$ 0.25	$ (0.09)	$ 0.24	$ 0.21	$ 0.26	$ 0.78	$ 0.89	$ 0.36
Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement									$ 0	$ 0	$ (12,923)
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									1,078,288	548,839	614,741
2017 Tax Cuts and Jobs Act [Member]
Deferred Federal Income Tax Expense (Benefit)									$ 0	$ 0	$ (59,944)