Income Taxes Effective tax rate reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 141,789	$ 151,368	$ 147,101
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate	49,626	52,979	51,485
Effective Income Tax Rate Reconciliation, Tax Exempt Income	(2,950)	(3,233)	(3,400)
Effective Income Tax Rate Reconciliation, Other Adjustments	(666)	(2,328)	(750)
Income Tax Expense (Benefit)	$ 46,010	$ 47,418	$ 47,335