Income Taxes - Components of Effective Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Amount
Statutory federal income tax	$ 41,382	$ 65,784	$ 48,482
Deferred tax asset revaluation	(8,721)	23,709	0
Tax-exempt income, net of interest expense disallowance	(3,104)	(5,065)	(5,439)
State income tax, net of federal income tax effect	8,846	5,069	4,323
Other	784	70	(1,195)
Total income tax expense	$ 39,187	$ 89,567	$ 46,171
% of Pretax Income
Statutory federal income tax rate (percent of pretax income)	21.00%	35.00%	35.00%
Revaluation of deferred tax assets (percent of pretax income)	(4.40%)	12.60%	0.00%
Tax-exempt income, net of interest expense disallowance (percent of pretax income)	(1.60%)	(2.70%)	(3.90%)
State income tax, net of federal income tax effect (percent of pretax income)	4.50%	2.70%	3.10%
Other (percent of pretax income)	0.40%	0.10%	(0.90%)
Effective tax rate	19.90%	47.70%	33.30%