Cash, Cash Equivalents, And Marketable Securities (Cash, Cash Equivalents, And Marketable Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cash	$ 81,462	$ 110,799
Money market funds	113,416	85,453
Time deposits	4,172	3,384
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	1,697,434	1,233,076
Available-for-sale Securities, Equity Securities	89	0
Total	1,896,573	1,432,712
Included in Cash and cash equivalents	187,286	191,608	$ 237,361	$ 339,223
Included in Marketable securities	1,697,523	1,233,076
Included in Other assets (Restricted cash)	$ 11,764	$ 8,028