Income Taxes (Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Amount
Tax at statutory rate	$ 5,016	$ 11,923	$ 29,400	$ 30,844
Changes resulting from:
Tax-exempt interest income	(1,321)	(1,033)	(3,599)	(2,809)
State taxes, net of federal benefit	(803)	0	(803)	0
Change in valuation allowance	(29)	0	(29)	0
Bank-owned life insurance adjustments	(169)	0	(524)	0
Director plan change in control	(525)	0	(525)	0
Income tax credits, net	(413)	(992)	(2,428)	(1,851)
Nondeductible transaction expenses	2,100	0	2,100	525
Other, net	(256)	(298)	708	91
Income tax provision (benefit)	$ 3,600	$ 9,600	$ 24,300	$ 26,800
Effective federal income tax rate (as a percent)	25.10%	28.20%	28.90%	30.40%