Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 5,903	$ 5,945
Accumulated depreciation of fixed assets	1,345,836	1,333,103
Accumulated amortization of intangibles	$ 64,738	$ 58,471
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, Authorized shares	5,000	5,000
Preferred stock, Shares issued	0	0
Preferred stock, Shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, Authorized shares	1,600,000	1,600,000
Common stock, Shares issued	418,377	416,178
Common stock, Shares outstanding	418,377	416,178