Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Accounts receivable, allowance for doubtful accounts	$ 6,932	$ 7,119
Property and equipment, accumulated depreciation	$ 373,011	$ 371,756
Preferred stock, shares issued	0us-gaap_PreferredStockSharesIssued	0us-gaap_PreferredStockSharesIssued
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares issued	191,120,214us-gaap_CommonStockSharesIssued	191,655,690us-gaap_CommonStockSharesIssued
Common stock, shares outstanding	191,120,214us-gaap_CommonStockSharesOutstanding	191,655,690us-gaap_CommonStockSharesOutstanding

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Face amount or stated value per share of common stock.

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