Restatement of Previously Issued Financial Statements (Impact on Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands		Jun. 30, 2016		Dec. 31, 2015		Jun. 30, 2015		Dec. 31, 2014
Current assets:
Cash and cash equivalents		$ 6,099	[1],[2]	$ 7,930	[1]	$ 5,949	[2]	$ 10,809	[2]
Accounts receivable	[1]	262,674		260,029
Deferred income taxes	[1]	19,279		20,891
Income tax receivable	[1]	24,893		20,663
Prepaid expenses and other current assets	[1]	23,595		37,051
Total current assets	[1]	336,540		346,564
Property and equipment	[1]	188,313		195,364
Other assets:
Goodwill	[1]	682,013		682,810
Intangible assets, net	[1]	71,407		75,694
Other noncurrent assets	[1]	8,396		7,321
Total other assets	[1]	761,816		765,825
Total assets	[1]	1,286,669		1,307,753
Current liabilities:
Current maturities of long-term debt	[1]	406,378		432,830
Accounts payable	[1]	133,423		116,166
Accrued expenses and other current liabilities	[1]	72,704		81,922
Total current liabilities	[1]	612,505		630,918
Long-term debt, net of current maturities		0		0
Long-term deferred tax liabilities	[1]	105,455		105,088
Other long-term liabilities	[1]	13,445		15,308
Total liabilities	[1]	731,405		751,314
Commitments and contingencies (Note 10)	[1]
Stockholders' investment:
Common stock	[1]	383		383
Additional paid-in capital	[1]	397,917		397,253
Retained earnings	[1]	156,964		158,803
Total stockholders’ investment	[1]	555,264		556,439
Total liabilities and stockholders’ investment	[1]	1,286,669		1,307,753
As Previously Reported
Current assets:
Cash and cash equivalents		7,792		8,664		6,463		11,345
Accounts receivable		273,554		272,176
Deferred income taxes		3,264		4,876
Income tax receivable		11,261		11,262
Prepaid expenses and other current assets		42,645		50,839
Total current assets		338,516		347,817
Property and equipment		193,104		197,744
Other assets:
Goodwill		691,687		691,118
Intangible assets, net		72,407		76,694
Other noncurrent assets		6,603		6,183
Total other assets		770,697		773,995
Total assets		1,302,317		1,319,556
Current liabilities:
Current maturities of long-term debt		15,000		15,000
Accounts payable		118,850		104,357
Accrued expenses and other current liabilities		40,088		48,657
Total current liabilities		173,938		168,014
Long-term debt, net of current maturities		391,378		417,830
Long-term deferred tax liabilities		104,767		104,400
Other long-term liabilities		13,400		16,005
Total liabilities		683,483		706,249
Commitments and contingencies (Note 10)
Stockholders' investment:
Common stock		383		383
Additional paid-in capital		397,917		397,253
Retained earnings		220,534		215,671
Total stockholders’ investment		618,834		613,307
Total liabilities and stockholders’ investment		1,302,317		1,319,556
Adjustments
Current assets:
Cash and cash equivalents		(1,693)		(734)		$ (514)		$ (536)
Adjustments | Receivables & Related Reserves
Current assets:
Cash and cash equivalents		0		0
Accounts receivable		(10,880)		(12,147)
Deferred income taxes		0		0
Income tax receivable		0		0
Prepaid expenses and other current assets		(1,139)		(112)
Total current assets		(12,019)		(12,259)
Property and equipment		0		0
Other assets:
Goodwill		(2,136)		(2,136)
Intangible assets, net		0		0
Other noncurrent assets		(326)		(230)
Total other assets		(2,462)		(2,366)
Total assets		(14,481)		(14,625)
Current liabilities:
Current maturities of long-term debt		0		0
Accounts payable		11,379		11,125
Accrued expenses and other current liabilities		467		288
Total current liabilities		11,846		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		11,846		11,413
Stockholders' investment:
Common stock		0		0
Additional paid-in capital		0		0
Retained earnings		(26,327)		(26,038)
Total stockholders’ investment		(26,327)		(26,038)
Total liabilities and stockholders’ investment		(14,481)		(14,625)
Adjustments | Unrecorded Charges & Contingent Liabilities
Current assets:
Cash and cash equivalents		(1,693)		(734)
Accounts receivable		0		0
Deferred income taxes		0		0
Income tax receivable		0		0
Prepaid expenses and other current assets		(12,308)		(10,464)
Total current assets		(14,001)		(11,198)
Property and equipment		302		302
Other assets:
Goodwill		(1,896)		(530)
Intangible assets, net		(1,000)		(1,000)
Other noncurrent assets		1,704		1,368
Total other assets		(1,192)		(162)
Total assets		(14,891)		(11,058)
Current liabilities:
Current maturities of long-term debt		0		0
Accounts payable		3,194		684
Accrued expenses and other current liabilities		13,928		15,225
Total current liabilities		17,122		15,909
Long-term debt, net of current maturities		0		0
Long-term deferred tax liabilities		0		0
Other long-term liabilities		45		(697)
Total liabilities		17,167		15,212
Stockholders' investment:
Common stock		0		0
Additional paid-in capital		0		0
Retained earnings		(32,058)		(26,270)
Total stockholders’ investment		(32,058)		(26,270)
Total liabilities and stockholders’ investment		(14,891)		(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		(2,721)		(2,405)
Total current assets		(2,721)		(2,405)
Property and equipment		0		0
Other assets:
Goodwill		0		0
Intangible assets, net		0		0
Other noncurrent assets		0		0
Total other assets		0		0
Total assets		(2,721)		(2,405)
Current liabilities:
Current maturities of long-term debt		0		0
Accounts payable		0		0
Accrued expenses and other current liabilities		18,113		17,644
Total current liabilities		18,113		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		18,113		17,644
Stockholders' investment:
Common stock		0		0
Additional paid-in capital		0		0
Retained earnings		(20,834)		(20,049)
Total stockholders’ investment		(20,834)		(20,049)
Total liabilities and stockholders’ investment		(2,721)		(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		(2,882)		(807)
Total current assets		(2,882)		(807)
Property and equipment		(5,093)		(2,682)
Other assets:
Goodwill		(9,626)		(9,626)
Intangible assets, net		0		0
Other noncurrent assets		415		0
Total other assets		(9,211)		(9,626)
Total assets		(17,186)		(13,115)
Current liabilities:
Current maturities of long-term 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		(17,186)		(13,115)
Total stockholders’ investment		(17,186)		(13,115)
Total liabilities and stockholders’ investment		(17,186)		(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		13,632		9,401
Prepaid expenses and other current assets		0		0
Total current assets		29,647		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		33,631		29,400
Current liabilities:
Current maturities of long-term debt		391,378		417,830
Accounts payable		0		0
Accrued expenses and other current liabilities		108		108
Total current liabilities		391,486		417,938
Long-term debt, net of current maturities		(391,378)		(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		32,835		28,604
Total stockholders’ investment		32,835		28,604
Total liabilities and stockholders’ investment		$ 33,631		$ 29,400

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

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