Income Taxes (Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. federal statutory tax rate	35.00%	35.00%	35.00%
Foreign rate differential	(11.00%)	(13.40%)	(12.20%)
Federal research credit	(2.00%)	(2.10%)	(1.80%)
Stock-based compensation expense	(3.40%)	0.30%	0.10%
Other adjustments	0.70%	(3.00%)	0.00%
Effective tax rate	19.30%	16.80%	21.10%