Income Taxes (Effective Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation, Amount
Tax at statutory rate									$ 52,548	$ 43,341	$ 31,367
Tax-exempt interest income									(5,320)	(3,943)	(3,142)
State taxes, net of federal benefit									13	0	0
Change in valuation allowance									(706)	0	0
Bank-owned life insurance adjustments									(832)	(124)	(95)
Director plan change in control									(508)	0	0
Income tax credits, net									(2,454)	(2,557)	(1,624)
Nondeductible transaction expenses									$ 2,100	$ 411	$ 403
Nondeductible transaction expenses									1.40%	0.30%	0.40%
Tax benefits in excess of compensation costs on share-based payments									$ (2,240)	$ 0	$ 0
Other, net									(495)	(128)	591
Income tax provision	$ 18,969	$ 2,848	$ 10,532	$ 9,757	$ 10,200	$ 9,600	$ 9,100	$ 8,100	$ 42,106	$ 37,000	$ 27,500
Effective Income Tax Rate, Tax Rate Reconciliation, Percent
Tax at statutory rate									35.00%	35.00%	35.00%
Tax-exempt interest income									(3.50%)	(3.20%)	(3.50%)
State taxes, net of federal benefit									0.00%	0.00%	0.00%
Change in valuation allowance									(0.50%)	0.00%	0.00%
Bank-owned life insurance adjustments									(0.60%)	(0.10%)	(0.10%)
Director plan change in control									(0.30%)	0.00%	0.00%
Income tax credits, net									(1.60%)	(2.10%)	(1.80%)
Tax benefits in excess of compensation costs on share-based payments									(1.50%)	(0.00%)	(0.00%)
Other, net									(0.40%)	0.00%	0.70%
Income tax expense									28.00%	29.90%	30.70%