Income Taxes - U.S. Federal Statutory Income Tax Rate Reconciled to Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefit	3.80%	3.80%	3.40%
Tax rate change	7.80%	1.50%	0.70%
Nondeductible transaction costs	0.90%		0.60%
Nondeductible meals, entertainment and penalties	4.30%	4.10%	0.90%
Stock-based compensation	4.50%	(0.10%)	0.10%
Uncertain tax positions	0.80%	(2.30%)	(0.20%)
Tax credits	(3.60%)	(4.30%)	(0.90%)
Other	(0.30%)	(0.10%)	(0.60%)
Effective Income Tax Rate Reconciliation, Percent, Total	53.20%	37.60%	39.00%