Fair Value Measurements Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments related to deferred compensation plan	$ 28,775	$ 23,542
Total assets	28,775	23,542
Deferred Compensation Liability, Current and Noncurrent	28,867	23,729
Fair value of contingent consideration payable	17,285	17,738
Total liabilities	46,152	41,467
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments related to deferred compensation plan	0	0
Total assets	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Fair value of contingent consideration payable	0	0
Total liabilities	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments related to deferred compensation plan	28,775	23,542
Total assets	28,775	23,542
Deferred Compensation Liability, Current and Noncurrent	28,867	23,729
Fair value of contingent consideration payable	0	0
Total liabilities	28,867	23,729
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments related to deferred compensation plan	0	0
Total assets	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Fair value of contingent consideration payable	17,285	17,738
Total liabilities	$ 17,285	$ 17,738