Employee Benefit Plans (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, employer contributions				$ 2,500,000	$ 2,000,000
Defined contribution plan, compensation expense	$ 900,000	$ 900,000		$ 2,100,000	$ 1,800,000
Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plans, estimated future employer contributions			$ 0