Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Taxes at statutory rate	21.00%	35.00%	35.00%
State taxes, net of federal benefit	5.20%	4.40%	3.90%
Foreign tax rate differential	0.50%	(0.30%)	(0.10%)
Tax legislation		(22.60%)
Other permanent differences	1.80%	0.70%	0.80%
Prior year tax adjustments	0.20%	(0.30%)	(1.00%)
Unrecognized tax benefits	(0.60%)	0.10%	1.00%
Valuation allowance	1.30%	0.70%	(0.30%)
Equity-based compensation	(3.00%)	(2.10%)	(1.00%)
Tax credits	(0.50%)	(0.60%)	(0.80%)
Taxes at effective rate	25.90%	15.00%	37.50%