Employment Expenses and Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Employer matching contribution, percent	100.00%
401(k) percent of match	4.00%
Annual contribution	$ 10,800	$ 9,900	$ 9,400
Stock purchase plan, percent of match	15.00%
Stock purchase plans compensation expense	$ 826	$ 835	$ 880