Income Taxes Tax Rate (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

A reconciliation of the differences between the effective tax rate and the federal statutory tax rate for the years ended December 31 is as follows:

	2017	2016	2015
Federal statutory tax rate	35.0%	35.0%	35.0%
State income taxes, net of federal income tax benefit	3.8	3.9	3.9
Non-deductible employee stock purchase plan expense	0.3	0.3	0.3
Non-deductible meals and entertainment	0.3	0.3	0.3
Tax Reform Act deferred tax revaluation and transition tax impact	(26.9)	—	—
Other, net	(1.4)	(0.3)	0.1
Effective tax rate	11.1%	39.2%	39.6%