CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Statement Of Financial Position [Abstract]
Allowances for accounts receivable	$ 6,095	$ 6,770
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,300,000,000	1,300,000,000
Common stock, shares outstanding	546,256,000	550,894,000