Income Taxes (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 194,156	$ 195,278	$ 168,047
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	33,729	32,896	29,009
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount	(15,510)	(13,992)	(8,274)
Income Tax Reconciliation Change In Cash Surrender Value Of Life Insurance	(1,853)	(1,544)	(884)
Income Tax Credits and Adjustments	(2,054)	(1,439)	(2,441)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Amount	1,781	1,257	1,005
Nondeductible acquisition-related expense	1,608	0	876
Deferred Tax Assets, Tax Deferred Expense	1,157	(2,268)	(5,529)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	(13,071)	8,689	2,917
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	(1,156)	0	0
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount	(1,874)	4,271	1,625
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations	$ 196,913	$ 205,770	$ 180,517