Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Business Segments (Narrative) (Details) (USD $)	3 Months Ended							9 Months Ended		12 Months Ended
Business Segments (Narrative) (Details) (USD $)	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2013 segments	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Number of reportable segments								6
Total operating revenues	$ 902,479,000	$ 889,596,000	$ 836,840,000	$ 895,891,000	$ 877,637,000	$ 854,430,000	$ 827,612,000	$ 2,628,915,000	$ 2,559,679,000	$ 3,455,570,000	$ 3,525,997,000
Kaplan International [Member] \| Related to certain items recorded in 2011 and 2010 [Member]
Prior periods adjustments									$ 3,900,000