Note 5 - Goodwill and Intangible Assets (Details) - Goodwill - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Goodwill [Line Items]
Goodwill balance	[1]	$ 495,679	$ 369,312
Goodwill acquired during the year	[1]	24,296	136,034
Adjustments to prior year acquisitions	[1]	200	(260)
Effect of foreign currency translation	[1]	(11,878)	(9,407)
Goodwill balance	[1]	508,297	495,679
UNITED STATES
Goodwill [Line Items]
Goodwill balance	[1]	401,560	273,070
Goodwill acquired during the year	[1]	10,742	128,426
Adjustments to prior year acquisitions	[1]	$ 200	$ 64
Effect of foreign currency translation	[1]
Goodwill balance	[1]	$ 412,502	$ 401,560
CANADA
Goodwill [Line Items]
Goodwill balance	[1]	17,178	$ 19,279
Goodwill acquired during the year	[1]	$ 222
Adjustments to prior year acquisitions	[1]
Effect of foreign currency translation	[1]	$ (2,036)	$ (2,101)
Goodwill balance	[1]	15,364	17,178
UNITED KINGDOM
Goodwill [Line Items]
Goodwill balance	[1]	38,354	39,593
Goodwill acquired during the year	[1]	$ 13,332	1,640
Adjustments to prior year acquisitions	[1]		(324)
Effect of foreign currency translation	[1]	$ (2,258)	(2,555)
Goodwill balance	[1]	49,428	38,354
AUSTRALIA
Goodwill [Line Items]
Goodwill balance	[1]	$ 38,587	37,370
Goodwill acquired during the year	[1]		$ 5,968
Adjustments to prior year acquisitions	[1]
Effect of foreign currency translation	[1]	$ (7,584)	$ (4,751)
Goodwill balance	[1]	$ 31,003	$ 38,587

[1] Goodwill recorded in connection with certain tax benefits to be realized in the Company's U.S. income tax returns has been reflected in the United States segment.