Income Taxes - Income Tax Reconciliation (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of provision for income taxes to the amount computed at the Federal statutory rate
Federal income tax at statutory rate, percent	35.00%	35.00%	35.00%
State taxes, net of Federal benefit, percent	4.30%	4.10%	4.20%
Goodwill impairment, percent	0.30%	0.20%	0.00%
Foreign rate differential, percent	(0.40%)	(0.40%)	(0.40%)
Miscellaneous, percent	(0.10%)	0.20%	0.10%
Effective income tax rate, Total percentage	39.10%	39.10%	38.90%