CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Accounts receivable, allowance	$ 265,797	$ 242,674
Property and equipment, accumulated depreciation	2,207,320	2,029,506
Intangibles, accumulated amortization	$ 706,413	$ 621,891
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, issued	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	450,000,000	450,000,000
Common stock, shares issued	216,533,208	215,640,968
Common stock, shares outstanding	215,466,069	215,640,968
Treasury stock, shares	1,067,139