Note 17 - Unaudited Quarterly Financial Data - Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from external customers	$ 4,214,614	$ 4,979,733	$ 4,727,356
Gross profit	718,012	784,947	756,046
Segment operating income	80,728	121,276	141,741
Segment income (loss) from continuing operations before taxes	66,449	107,803	130,543
Net income	$ 40,582	$ 66,053	$ 79,957
Earnings per common share:
Basic (in dollars per share)	$ 1.02	$ 1.64	$ 2.01
Diluted (in dollars per share)	$ 1	$ 1.61	$ 1.96
Revenues from external customers	$ 4,214,614	$ 4,979,733	$ 4,727,356
Gross profit	718,012	784,947	756,046
Segment operating income	80,728	121,276	141,741
Segment income (loss) from continuing operations before taxes	66,449	107,803	130,543
Net income	40,582	66,053	$ 79,957
First Quarter [Member]
Revenues from external customers	1,070,840	1,193,535
Gross profit	183,270	193,622
Segment operating income	8,181	30,329
Segment income (loss) from continuing operations before taxes	3,942	27,388
Net income	$ 2,395	$ 16,781
Earnings per common share:
Basic (in dollars per share)	$ 0.06	$ 0.42
Diluted (in dollars per share)	$ 0.06	$ 0.41
Revenues from external customers	$ 1,070,840	$ 1,193,535
Gross profit	183,270	193,622
Segment operating income	8,181	30,329
Segment income (loss) from continuing operations before taxes	3,942	27,388
Net income	2,395	16,781
Second Quarter [Member]
Revenues from external customers	1,026,462	917,878
Gross profit	180,478	207,633
Segment operating income	21,572	35,560
Segment income (loss) from continuing operations before taxes	17,809	31,962
Net income	$ 10,817	$ 19,576
Earnings per common share:
Basic (in dollars per share)	$ 0.27	$ 0.49
Diluted (in dollars per share)	$ 0.27	$ 0.48
Revenues from external customers	$ 1,026,462	$ 917,878
Gross profit	180,478	207,633
Segment operating income	21,572	35,560
Segment income (loss) from continuing operations before taxes	17,809	31,962
Net income	10,817	19,576
Third Quarter [Member]
Revenues from external customers	1,096,041	1,294,076
Gross profit	181,316	208,008
Segment operating income	27,588	36,030
Segment income (loss) from continuing operations before taxes	24,303	32,462
Net income	$ 14,880	$ 19,883
Earnings per common share:
Basic (in dollars per share)	$ 0.38	$ 0.49
Diluted (in dollars per share)	$ 0.37	$ 0.48
Revenues from external customers	$ 1,096,041	$ 1,294,076
Gross profit	181,316	208,008
Segment operating income	27,588	36,030
Segment income (loss) from continuing operations before taxes	24,303	32,462
Net income	14,880	19,883
Fourth Quarter [Member]
Revenues from external customers	1,021,271	1,161,819
Gross profit	172,948	175,684
Segment operating income	23,387	19,357
Segment income (loss) from continuing operations before taxes	20,395	15,991
Net income	$ 12,490	$ 9,813
Earnings per common share:
Basic (in dollars per share)	$ 0.32	$ 0.24
Diluted (in dollars per share)	$ 0.31	$ 0.24
Revenues from external customers	$ 1,021,271	$ 1,161,819
Gross profit	172,948	175,684
Segment operating income	23,387	19,357
Segment income (loss) from continuing operations before taxes	20,395	15,991
Net income	$ 12,490	$ 9,813