Income Taxes - Income tax rate reconciliation (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State and other taxes, net of federal tax benefit	2.70%	2.80%	2.40%
Change in unrecognized tax benefits	0.50%	0.80%	2.40%
Domestic production activity deduction	(0.60%)	(0.70%)	(6.00%)
Research and experimentation tax credit	(0.10%)	0.10%	(3.40%)
State adjustments including audits and settlements	(0.10%)	(0.20%)	(1.10%)
Compensation related tax credits, net of deduction offsets	(0.10%)	(0.20%)	(0.80%)
Changes in tax rates and state tax laws	(1.90%)	(0.00%)	(0.00%)
Other	0.60%	0.20%	0.80%
Effective tax rate	36.00%	37.80%	29.30%