Income Taxes - Difference of Income Taxes from Statutory Federal Income Tax Rates (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal U.S. income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal tax benefit	4.20%	4.20%	4.30%
Non-deductible expenses	0.50%	0.60%	0.70%
Non-U.S. income taxed at different rates, net of foreign tax credits	0.10%	(0.20%)	(1.00%)
Federal tax credits	(0.60%)	(0.60%)	(1.30%)
Tax impact of uncertain tax positions	(0.20%)	(0.10%)	0.10%
Valuation allowance release, net	(0.50%)	(0.30%)	(1.00%)
Other, net	(0.10%)	(0.10%)	(0.20%)
Effective tax rate	38.40%	38.50%	36.60%