Employee Benefit And Stock Compensation Plans - Narrative II (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Benefit and Stock Compensation Plans
Employer matching contribution, percent	4.50%	3.00%	4.50%
Employer contributions charged to expense	$ 1.8	$ 1.3	$ 1.5