Commitments and Contingencies - Rent Expense on Operating Leases (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 311,652	$ 308,561	$ 276,030
Sublease proceeds	(3,808)	(4,700)	(7,090)
Net rent expense	$ 307,844	$ 303,861	$ 268,940

The amount of revenue recognized for the period under subleasing arrangements.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 55

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6584307&loc=d3e41620-112719

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

-Publisher FASB

-Name FASB Technical Bulletin (FTB)

-Number 88-1

-Paragraph 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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