Income Taxes Income tax rate reconciliation (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State and other taxes, net of federal tax benefit	2.40%	2.90%	2.80%
Change in unrecognized tax benefits	2.40%	1.40%	(0.20%)
Change in valuation allowance	0.00%	(2.70%)	0.70%
Domestic production activity deduction	(6.00%)	0.00%	0.00%
Research and experimentation tax credit	(3.40%)	0.00%	0.00%
State adjustments including audits and settlements	(1.10%)	(1.10%)	0.20%
Compensation related tax credits, net of deduction offsets	(0.80%)	(0.60%)	(0.90%)
Changes in tax rates and state tax laws	0.00%	0.00%	(3.20%)
Other	0.80%	0.00%	0.10%
Effective tax rate	29.30%	34.90%	34.50%