CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Student receivables, allowance for doubtful accounts, current	$ 31,813	$ 35,111
Student receivables, allowance for doubtful accounts, non-current	$ 9,177	$ 11,982
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	81,808,424	81,616,987
Common stock, shares outstanding	67,090,083	67,069,734
Treasury, Shares in treasury	14,718,341	14,547,253