Income Taxes - Income Tax Reconciliation (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Income Tax Expense
Expected provision at federal statutory tax rate	35.00%	35.00%	35.00%
State tax expense, net of federal benefit	1.60%	1.70%	1.00%
Income tax credits	(0.00%)	(0.00%)	(0.40%)
Other	0.30%	0.20%	0.50%
Total income tax expense (benefit)	36.90%	36.90%	36.10%