Fair Value Measurement - Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Cash Equivalents, at Carrying Value [Abstract]
Cash equivalents	$ 50,006	$ 60,618	$ 50,148
Cash	171,779	195,343	117,026
Total cash and cash equivalents	$ 221,785	$ 255,961	$ 167,174	$ 229,121