Summary of Significant Accounting Policies (Cash and Equivalents) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 93,108	$ 32,335	$ 119,471	$ 17,399
Cash [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	29,569	4,481
Money market funds [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	14,950	20,354
Government-backed security [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	20,000	7,500
Asset-backed Securities [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	8,185	0
Corporate debt securities [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 20,404	$ 0