Significant Accounting Policies (Property and Equipment) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Total property and equipment, net	$ 338,996,000	$ 303,294,000
Retirement of property and equipment	10,300,000	5,300,000
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, gross	85,092,000	76,202,000
Estimated useful lives of property and equipment	40 years
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	204,110,000	178,948,000
Estimated useful lives of property and equipment	3 years
Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	316,902,000	259,225,000
Estimated useful lives of property and equipment	3 years
Equipment and furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	105,145,000	86,362,000
Estimated useful lives of property and equipment	7 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	168,990,000	149,731,000
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	10 years
Depreciable assets
Property, Plant and Equipment [Line Items]
Property and equipment, gross	880,239,000	750,468,000
Less accumulated depreciation and amortization	(597,268,000)	(479,460,000)
Assets under construction
Property, Plant and Equipment [Line Items]
Property and equipment, gross	28,438,000	15,517,000
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 27,587,000	$ 16,769,000