Employee Benefit Plans (Schedule of RSU Activity) (Details) - RSUs shares in Thousands	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Number of shares
Beginning balance (in shares) | shares	1,130
Granted (in shares) | shares	933
Vested (in shares) | shares	(410)
Cancelled (in shares) | shares	(53)
Ending balance (in shares) | shares	1,600
Weighted Average Grant Date Fair Value Per Share
Beginning Balance (in dollars per share) | $ / shares	$ 43.22
Granted (in dollars per share) | $ / shares	68.27
Vested (in dollars per share) | $ / shares	40.94
Cancelled (in dollars per share) | $ / shares	54.78
Ending Balance (in dollars per share) | $ / shares	$ 58.04