Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Impairment of goodwill									$ 0	$ 0	$ 52,585
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements									0	(6,700)	0
REVENUES	$ 181,581	$ 142,305	$ 148,353	$ 147,025	$ 157,938	$ 138,443	$ 149,618	$ 143,593	619,264	589,592	580,023
Income (Loss) from Continuing Operations before Interest Expense, Interest Income, Income Taxes, Extraordinary Items, Noncontrolling Interests, Net	22,550	12,917	19,794	17,529	14,285	18,287	18,117	13,836
Net earnings (loss) from continuing operations	13,343	6,347	10,570	8,895	6,659	9,595	9,298	6,522	39,155	32,074	(19,625)
EARNINGS (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAXES	$ 1,425	$ 214	$ 214	$ 214	$ (2,948)	$ 312	$ 211	$ 211	$ 2,067	$ (2,214)	$ (3)
Weighted average shares:
Basic (in shares)	63,742	64,239	64,541	64,454	64,289	64,286	64,285	64,148	64,242	64,253	63,992
Diluted (in shares)	64,536	65,171	65,471	65,337	65,222	65,271	65,207	65,141	65,127	65,211	63,992
Earnings (loss) per share from continuing operations
Basic (in dollars per share)	$ 0.21	$ 0.10	$ 0.16	$ 0.14	$ 0.10	$ 0.15	$ 0.14	$ 0.10	$ 0.61	$ 0.50	$ (0.31)
Diluted (in dollars per share)	$ 0.21	$ 0.10	$ 0.16	$ 0.14	$ 0.10	$ 0.15	$ 0.14	$ 0.10	$ 0.60	$ 0.49	$ (0.31)
Pension Plans [Member]
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements									$ 0	$ (11,660)	$ 0
Pension Plans [Member] | Continuing Operations [Member]
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements										6,700
Pension Plans [Member] | Discontinued Operations [Member]
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements										4,960
ACMI Services [Member]
Impairment of goodwill									0	0	52,585
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements					$ 6,700				0		0
REVENUES									$ 433,109	$ 439,919	$ 444,504