Saving and Retirement Plans 401K Retirement Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Current Fiscal Year End Date	--12-31
Profit Sharing Contribution, Vesting Period	3 years
Defined Contribution Plan, Cost Recognized	$ 4,100,000	$ 3,300,000	$ 3,100,000
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 5,000