Cash, Cash Equivalents and Available-for-sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Cash, Cash Equivalents, and Short-term Investments [Abstract]
Cash and cash equivalents	$ 141,219	$ 61,653	$ 61,695	$ 146,470
Available-for-sale securities	$ 0	$ 50,097