Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Revenues	$ 1,713,737	$ 1,861,386
Cost of services (including depreciation)	1,510,424	1,623,480
Gross profit	203,313	237,906
Selling, general and administrative expenses	158,524	145,463
Amortization of intangible assets	7,495	8,293
Operating income	37,294	84,150
Interest expense	(3,589)	(1,400)
Interest income	516	453
Equity in losses of unconsolidated affiliates	(181)
Other income (expense), net	262	(212)
Income from continuing operations before income taxes	34,302	82,991
Provision for income taxes	13,443	30,601
Net income from continuing operations	20,859	52,390
Net income from discontinued operations		5,795
Net income	20,859	58,185
Less: Net income attributable to non-controlling interests	363	4,701
Net income attributable to common stock	20,496	53,484
Amounts attributable to common stock:
Net income from continuing operations	20,496	47,689
Net income from discontinued operations		5,795
Net income attributable to common stock	$ 20,496	$ 53,484
Earnings per share attributable to common stock - basic and diluted:
Continuing operations	$ 0.13	$ 0.22
Discontinued operations		0.03
Net income attributable to common stock	$ 0.13	$ 0.25
Shares used in computing earnings per share:
Weighted average basic shares outstanding	162,803	215,473
Weighted average diluted shares outstanding	162,806	215,490