Fair Value Measurements - Assets Measured at Fair Value On A Recurring Basis (Details) (Fair Value, Measurements, Recurring [Member], Fair Value, Inputs, Level 1 [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	$ 61,311	$ 38,823
Cash equivalents	64,577	65,708
Total cash and cash equivalents	$ 125,888	$ 104,531