Fair Value Measurements - Liability Measured on Recurring Basis, Unobservable Input Reconciliation (Details) (Contingent Consideration, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Contingent Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 6,697	$ 1,290
Contingent consideration liability recorded as the result of acquisitions (see Note 2)	0	4,704
Initial purchase price adjustments finalized over the period (see Note 2)	0	280
Fair value adjustments recorded to (income) expense during the period	(4,094)	480
Contingent payments made	(77)	(57)
Ending balance	$ 2,526	$ 6,697