Income Taxes - Effective Rate (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Statutory U.S. federal income tax rate	35.00%	35.00%	35.00%
Statutory U.S. federal income tax rate	1.60%	1.60%	1.50%
Benefits and taxes related to foreign operations	(6.20%)	(7.20%)	(8.50%)
Unrecognized tax positions	(0.40%)	(0.20%)	0.10%
Adjustment to current and deferred taxes, prior years	0.00%	0.00%	(0.50%)
Other	0.10%	(0.60%)	0.90%
Effective income tax rates	30.10%	28.60%	28.50%