Restatement of Previously Issued Financial Statements (Impact on Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands		Mar. 31, 2016		Dec. 31, 2015		Mar. 31, 2015		Dec. 31, 2014
Current assets:
Cash and cash equivalents		$ 6,868	[1],[2]	$ 7,930	[1]	$ 11,408	[2]	$ 10,809	[2]
Accounts receivable	[1]	258,797		260,029
Deferred income taxes	[1]	20,338		20,891
Income tax receivable	[1]	21,289		20,663
Prepaid expenses and other current assets	[1]	32,404		37,051
Total current assets	[1]	339,696		346,564
Property and equipment	[1]	193,540		195,364
Other assets:
Goodwill	[1]	683,379		682,810
Intangible assets, net	[1]	73,547		75,694
Other noncurrent assets	[1]	7,920		7,321
Total other assets	[1]	764,846		765,825
Total assets	[1]	1,298,082		1,307,753
Current liabilities:
Current maturities of debt	[1]	416,110		432,830
Accounts payable	[1]	125,242		116,166
Accrued expenses and other current liabilities	[1]	79,491		81,922
Total current liabilities	[1]	620,843		630,918
Long-term debt, net of current maturities		0		0
Long-term deferred tax liabilities		105,455		105,088
Other long-term liabilities	[1]	14,313		15,308
Total liabilities	[1]	740,611		751,314
Commitments and contingencies (Note 10)	[1]
Stockholders’ investment:
Common stock	[1]	383		383
Additional paid-in capital	[1]	397,385		397,253
Retained earnings	[1]	159,703		158,803
Total stockholders’ investment	[1]	557,471		556,439
Total liabilities and stockholders’ investment	[1]	1,298,082		1,307,753
As Previously Reported
Current assets:
Cash and cash equivalents		8,064		8,664		11,984		11,345
Accounts receivable		268,441		272,176
Deferred income taxes		4,323		4,876
Income tax receivable		10,523		11,262
Prepaid expenses and other current assets		49,819		50,839
Total current assets		341,170		347,817
Property and equipment		197,353		197,744
Other assets:
Goodwill		691,687		691,118
Intangible assets, net		74,547		76,694
Other noncurrent assets		5,828		6,183
Total other assets		772,062		773,995
Total assets		1,310,585		1,319,556
Current liabilities:
Current maturities of debt		15,000		15,000
Accounts payable		111,362		104,357
Accrued expenses and other current liabilities		47,729		48,657
Total current liabilities		174,091		168,014
Long-term debt, net of current maturities		401,110		417,830
Long-term deferred tax liabilities		104,767		104,400
Other long-term liabilities		14,113		16,005
Total liabilities		694,081		706,249
Commitments and contingencies (Note 10)
Stockholders’ investment:
Common stock		383		383
Additional paid-in capital		397,385		397,253
Retained earnings		218,736		215,671
Total stockholders’ investment		616,504		613,307
Total liabilities and stockholders’ investment		1,310,585		1,319,556
Adjustments
Current assets:
Cash and cash equivalents		(1,196)		(734)		$ (576)		$ (536)
Adjustments | Receivables & Related Reserves
Current assets:
Cash and cash equivalents		0		0
Accounts receivable		(9,644)		(12,147)
Deferred income taxes		0		0
Income tax receivable		0		0
Prepaid expenses and other current assets		(1,277)		(112)
Total current assets		(10,921)		(12,259)
Property and equipment		0		0
Other assets:
Goodwill		(2,136)		(2,136)
Intangible assets, net		0		0
Other noncurrent assets		(230)		(230)
Total other assets		(2,366)		(2,366)
Total assets		(13,287)		(14,625)
Current liabilities:
Current maturities of debt		0		0
Accounts payable		10,970		11,125
Accrued expenses and other current liabilities		420		288
Total current liabilities		11,390		11,413
Long-term debt, net of current maturities		0		0
Long-term deferred tax liabilities		0		0
Other long-term liabilities		0		0
Total liabilities		11,390		11,413
Stockholders’ investment:
Common stock		0		0
Additional paid-in capital		0		0
Retained earnings		(24,677)		(26,038)
Total stockholders’ investment		(24,677)		(26,038)
Total liabilities and stockholders’ investment		(13,287)		(14,625)
Adjustments | Unrecorded Charges & Contingent Liabilities
Current assets:
Cash and cash equivalents		(1,196)		(734)
Accounts receivable				0
Deferred income taxes		0		0
Income tax receivable		0		0
Prepaid expenses and other current assets		(11,692)		(10,464)
Total current assets		(12,888)		(11,198)
Property and equipment		302		302
Other assets:
Goodwill		(530)		(530)
Intangible assets, net		(1,000)		(1,000)
Other noncurrent assets		2,157		1,368
Total other assets		627		(162)
Total assets		(11,959)		(11,058)
Current liabilities:
Current maturities of debt		0		0
Accounts payable		2,910		684
Accrued expenses and other current liabilities		12,548		15,225
Total current liabilities		15,458		15,909
Long-term debt, net of current maturities		0		0
Long-term deferred tax liabilities		0		0
Other long-term liabilities		200		(697)
Total liabilities		15,658		15,212
Stockholders’ investment:
Common stock		0		0
Additional paid-in capital		0		0
Retained earnings		(27,617)		(26,270)
Total stockholders’ investment		(27,617)		(26,270)
Total liabilities and stockholders’ investment		(11,959)		(11,058)
Adjustments | Insurance Reserves & Related Receivables
Current assets:
Cash and cash equivalents		0		0
Accounts receivable		0		0
Deferred income taxes		0		0
Income tax receivable		0		0
Prepaid expenses and other current assets		(2,642)		(2,405)
Total current assets		(2,642)		(2,405)
Property and equipment		0		0
Other assets:
Goodwill				0
Intangible assets, net		0		0
Other noncurrent assets		0		0
Total other assets		0		0
Total assets		(2,642)		(2,405)
Current liabilities:
Current maturities of debt		0		0
Accounts payable		0		0
Accrued expenses and other current liabilities		18,686		17,644
Total current liabilities		18,686		17,644
Long-term debt, net of current maturities		0		0
Long-term deferred tax liabilities		0		0
Other long-term liabilities		0		0
Total liabilities		18,686		17,644
Stockholders’ investment:
Common stock		0		0
Additional paid-in capital		0		0
Retained earnings		(21,328)		(20,049)
Total stockholders’ investment		(21,328)		(20,049)
Total liabilities and stockholders’ investment		(2,642)		(2,405)
Adjustments | Capital Improvements & Aircraft Spare Parts
Current assets:
Cash and cash equivalents		0		0
Accounts receivable		0		0
Deferred income taxes		0		0
Income tax receivable		0		0
Prepaid expenses and other current assets		(1,804)		(807)
Total current assets		(1,804)		(807)
Property and equipment		(4,115)		(2,682)
Other assets:
Goodwill		(9,626)		(9,626)
Intangible assets, net		0		0
Other noncurrent assets		165		0
Total other assets		(9,461)		(9,626)
Total assets		(15,380)		(13,115)
Current liabilities:
Current maturities of debt		0		0
Accounts payable		0		0
Accrued expenses and other current liabilities		0		0
Total current liabilities		0		0
Long-term debt, net of current maturities		0		0
Long-term deferred tax liabilities		0		0
Other long-term liabilities		0		0
Total liabilities		0		0
Stockholders’ investment:
Common stock		0		0
Additional paid-in capital		0		0
Retained earnings		(15,380)		(13,115)
Total stockholders’ investment		(15,380)		(13,115)
Total liabilities and stockholders’ investment		(15,380)		(13,115)
Adjustments | Income Taxes & Debt Reclassification
Current assets:
Cash and cash equivalents		0		0
Accounts receivable		0		0
Deferred income taxes		16,015		16,015
Income tax receivable		10,766		9,401
Prepaid expenses and other current assets		0		0
Total current assets		26,781		25,416
Property and equipment		0		0
Other assets:
Goodwill		3,984		3,984
Intangible assets, net		0		0
Other noncurrent assets		0		0
Total other assets		3,984		3,984
Total assets		30,765		29,400
Current liabilities:
Current maturities of debt		401,110		417,830
Accounts payable		0		0
Accrued expenses and other current liabilities		108		108
Total current liabilities		401,218		417,938
Long-term debt, net of current maturities		(401,110)		(417,830)
Long-term deferred tax liabilities		688		688
Other long-term liabilities		0		0
Total liabilities		796		796
Stockholders’ investment:
Common stock		0		0
Additional paid-in capital		0		0
Retained earnings		29,969		28,604
Total stockholders’ investment		29,969		28,604
Total liabilities and stockholders’ investment		$ 30,765		$ 29,400

[1] See Note 13 “Restatement of Previously Issued Financial Statements

[2] See Note 13 “Restatement of Previously Issued Financial Statements.”