Income Taxes Income tax rate reconciliation (Details)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State and other taxes, net of federal tax benefit	2.90%	2.80%	3.70%
Change in unrecognized tax benefits	1.40%	(0.20%)	(4.00%)
Change in valuation allowance	(2.70%)	0.70%	1.70%
State adjustments including audits and settlements	(1.10%)	0.20%	0.20%
Compensation related tax credits, net of deduction offsets	(0.60%)	(0.90%)	(4.90%)
Changes in tax rates and state tax laws	0.00%	(3.20%)	(3.90%)
Kansas High Performance Incentive Program credits	0.00%	0.00%	0.50%
Other	0.00%	0.10%	0.10%
Effective tax rate	34.90%	34.50%	28.40%