Summary of Changes in Classifications of Assets and Liabilities of Consolidated Entities (Details) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents		$ 98,758	$ 164,188	$ 35,972	$ 50,007
Accounts receivable, net		1,194,868	944,219
Inventories		27,791	25,702
Other		61,054	41,598
Current assets		1,500,899	1,307,671
Property and equipment, net		971,996	902,104
Goodwill		2,669,810	997,597	$ 992,102
Intangible assets, net		755,655	400,700
Other		292,846	236,807
Total assets	[1]	6,518,936	5,652,964
Current liabilities:
Accounts payable		187,061	175,725
Salaries, wages and other compensation		404,925	358,857
Other accrued liabilities		394,246	189,980
Long-term debt due within one year		24,630	24,607
Current liabilities		1,111,212	857,263
Long-term debt		3,137,025	$ 2,852,531
Variable Interest Entity, Primary Beneficiary
Current assets:
Cash and cash equivalents		36,798
Accounts receivable, net		36,085
Inventories		1,576
Other		3,001
Current assets		77,460
Property and equipment, net		17,100
Goodwill		271,717
Intangible assets, net		22,675
Other		54
Total assets		389,006
Current liabilities:
Accounts payable		26,291
Salaries, wages and other compensation		3,261
Other accrued liabilities		2,784
Long-term debt due within one year		1,106
Current liabilities		33,442
Long-term debt		1,274
Deferred credits and other liabilities		4,971
Total liabilities		$ 39,687

[1] The Company’s consolidated assets as of December 31, 2015 include total assets of variable interest entities of $389 million, which can only be used to settle the obligations of the variable interest entities. The Company’s consolidated liabilities as of December 31, 2015 include total liabilities of variable interest entities of $40 million. See note 1 of the notes to consolidated financial statements.