Income Taxes (Tables)
 3 Months Ended
Mar. 31, 2018
Income Tax Disclosure [Abstract]  
Reconciliation of provision for income taxes
The following is a reconciliation of income taxes at the statutory rate of 21% and 35% for 2018 and 2017, respectively, to the effective provision for income taxes as shown in the Consolidated Statements of Earnings ($ in thousands):
 
Three months ended
 
March 31,
 
2018
 
2017
Earnings before income taxes
$
24,937

 
$
14,868

Income taxes at statutory rate
5,237

 
5,204

Effect of:
 
 
 
Dividends-received deduction
(25
)
 
(79
)
Tax-exempt interest
(279
)
 
(633
)
Other
(80
)
 
(134
)
Provision for income taxes as shown on the Consolidated Statements of Earnings
$
4,853

 
$
4,358

GAAP effective tax rate
19.5
%
 
29.3
%