Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Statement Of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 21,763	$ 22,416
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	475,000,000	475,000,000
Common stock, shares issued	118,671,070	118,206,262
Common stock, shares outstanding	82,936,578	82,471,770
Treasury stock ,shares	35,734,492	35,734,492