Note 2 - Summary of Significant Accounting Policies - Effect of Accounting Policy Adoption (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	Dec. 31, 2015
Operating revenues	$ 469,222		$ 460,227		$ 449,758		$ 425,708		$ 431,233	$ 390,126	$ 370,350	$ 363,676	$ 1,804,915	$ 1,555,385	$ 1,451,205
Total operating expenses													1,726,009	1,526,777	1,423,474
Operating income	21,142	[1]	22,892	[1]	20,018	[1]	14,854	[1]	12,457	11,534	2,689	1,928	78,906	28,608	27,731
Income (loss) before Income Taxes													33,966	(21,124)	(24,422)
Income tax provision (benefit)													7,860	(17,187)	(8,448)
Net income (loss)													26,106	(3,937)	(15,974)
Net income (loss) attributable to common stockholders	$ 6,996	[1],[2]	$ 16,129	[1],[2]	$ 615	[1],[2]	$ 1,159	[1],[2]	$ 9,499	$ (675)	$ (8,452)	$ (4,432)	$ 24,899	$ (4,060)	$ (16,524)
Basic earnings (loss) per share (in dollars per share)	$ 0.14		$ 0.33		$ 0.04		$ 0.18		$ 1.49	$ (0.11)	$ (1.32)	$ (0.69)	$ 0.84	$ (0.64)	$ (2.59)
Basic weighted average of outstanding shares of common stock (in shares)													29,470	6,385	6,385
Diluted earnings (loss) per share (in dollars per share)	$ 0.14		$ 0.33		$ 0.04		$ 0.18		$ 1.49	$ (0.11)	$ (1.32)	$ (0.69)	$ 0.83	$ (0.64)	$ (2.59)
Diluted weighted average of outstanding shares of common stock (in shares)													30,133	6,385	6,385
Customer receivables	$ 190,254								$ 186,407				$ 190,254	$ 186,407
Other current assets	13,374								12,170				13,374	12,170
Total current assets	285,534								248,720				285,534	248,720
Total assets	910,487								820,571				910,487	820,571
Accounts payable	63,808								80,555				63,808	80,555
Other accrued liabilities	8,120								13,901				8,120	13,901
Deferred income taxes	19,978								15,630				19,978	15,630
Accumulated deficit	(17,335)								(43,459)				(17,335)	(43,459)
Stockholders' equity (deficit)	234,891								(43,394)				234,891	(43,394)
Total stockholder's equity (deficit)	238,387								(41,105)				238,387	(41,105)	$ (37,168)	$ (21,194)
Total liabilities, redeemable restricted units and stockholder's equity (deficit)	910,487								820,571				910,487	820,571
Receivables													(8,972)	(32,051)	13,114
Other assets													(3,438)	(529)	(1,857)
Accounts payable and other accrued liabilities													(21,020)	41,930	10,291
Deferred income tax provision													5,691	(20,156)	$ (12,245)
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Operating revenues													1,805,860
Total operating expenses													1,727,856
Operating income													78,004
Income (loss) before Income Taxes													33,064
Income tax provision (benefit)													7,598
Net income (loss)													25,466
Net income (loss) attributable to common stockholders													$ 24,259
Basic earnings (loss) per share (in dollars per share)													$ 0.82
Basic weighted average of outstanding shares of common stock (in shares)													29,470
Diluted earnings (loss) per share (in dollars per share)													$ 0.81
Diluted weighted average of outstanding shares of common stock (in shares)													30,133
Customer receivables	187,348												$ 187,348
Other current assets	11,562												11,562
Total current assets	280,816												280,816
Total assets	905,769												905,769
Accounts payable	61,916												61,916
Other accrued liabilities	7,771												7,771
Deferred income taxes	19,600												19,600
Accumulated deficit	(19,434)												(19,434)
Stockholders' equity (deficit)	232,792												232,792
Total stockholder's equity (deficit)	236,288												236,288
Total liabilities, redeemable restricted units and stockholder's equity (deficit)	905,769												905,769
Receivables													(9,917)
Other assets													(2,090)
Accounts payable and other accrued liabilities													(20,521)
Deferred income tax provision													5,429
Accounting Standards Update 2014-09 [Member]
Accumulated deficit									$ 1,500					$ 1,500
Accounting Standards Update 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Operating revenues													(945)
Total operating expenses													(1,847)
Operating income													902
Income (loss) before Income Taxes													902
Income tax provision (benefit)													262
Net income (loss)													640
Net income (loss) attributable to common stockholders													$ 640
Basic earnings (loss) per share (in dollars per share)													$ 0.02
Basic weighted average of outstanding shares of common stock (in shares)													29,470
Diluted earnings (loss) per share (in dollars per share)													$ 0.02
Diluted weighted average of outstanding shares of common stock (in shares)													30,133
Customer receivables	2,906												$ 2,906
Other current assets	1,812												1,812
Total current assets	4,718												4,718
Total assets	4,718												4,718
Accounts payable	1,892												1,892
Other accrued liabilities	349												349
Deferred income taxes	378												378
Accumulated deficit	2,099												2,099
Stockholders' equity (deficit)	2,099												2,099
Total stockholder's equity (deficit)	2,099												2,099
Total liabilities, redeemable restricted units and stockholder's equity (deficit)	$ 4,718												4,718
Receivables													945
Other assets													(1,348)
Accounts payable and other accrued liabilities													(499)
Deferred income tax provision													$ 262

[1] Fourth quarter 2018 results include an impairment charge of $10.7 million related to assets of business held for sale.

[2] Fourth quarter 2018 results include an impairment charge of $1.8 million related to equity method investments.