Income Taxes - Narratives (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Rate	Jun. 30, 2013 Rate
Income Tax Examination [Line Items]
Effective Income Tax Rate, Continuing Operations		33.00%	31.00%
Effective Income Tax Rate Reconciliation, Tax Contingencies		2.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount		1.00%
Unrecognized Tax Benefits		$ 500,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense		200,000
Income Tax Examination, Likelihood of Unfavorable Settlement	P12M
Income Taxes Paid		18,010,000	17,769,000
Canada [Member]
Income Tax Examination [Line Items]
Income Tax Examination, Liability (Refund) Adjustment from Settlement with Taxing Authority	$ 4,000,000	$ 4,000,000
Civil penalty [Member]
Income Tax Examination [Line Items]
Effective Income Tax Rate Reconciliation, Other Adjustments		1.00%
Mexican CNA water tax [Member]
Income Tax Examination [Line Items]
Effective Income Tax Rate Reconciliation, Other Adjustments		3.00%