Summary of Significant Accounting Policies (Cash and Equivalents) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 89,395	$ 93,108	$ 167,384	$ 32,335
Cash [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	10,309	29,569
Money market funds [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	57,086	14,950
Government-backed security [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	22,000	20,000
Asset-backed Securities [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	0	8,185
Corporate debt securities [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 0	$ 20,404