Income Taxes - Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal income tax rate	35.00%	35.00%	35.00%
State income taxes, net of Federal tax effect	3.80%	6.80%	6.10%
Non-deductible compensation and meals and entertainment	0.70%	1.20%	0.70%
Tax credits	(2.20%)	(2.10%)	(1.00%)
Valuation allowance on foreign tax credit	2.50%	0.00%	0.00%
Enactment of TCJA	9.10%	0.00%	0.00%
Other	(0.80%)	0.50%	(0.50%)
Effective tax rate	48.10%	41.40%	40.30%