Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of income tax expense

The following table shows the composition of income tax expense.

Year Ended December 31 (Dollars in thousands)	2017			2016		2015
Current:
Federal	$	26,012		$	25,479	$	26,092
State	4,530			3,005		3,365
Total current	30,542			28,484		29,457
Deferred:
Federal	5,869			2,530		1,577
State	(488		)	326		43
Deferred tax liability remeasurement	(2,614		)	—		—
Total deferred	2,767			2,856		1,620
Total provision	$	33,309		$	31,340	$	31,077

Schedule of reasons for the difference between income tax expense and the amount computed by applying the statutory federal income tax rate

The following table shows the reasons for the difference between income tax expense and the amount computed by applying the statutory federal income tax rate (35%) to income before income taxes.

	2017					2016					2015
Year Ended December 31 (Dollars in thousands)	Amount			Percent of Pretax Income		Amount			Percent of Pretax Income		Amount			Percent of Pretax Income
Statutory federal income tax	$	35,476		35.0	%	$	31,194		35.0	%	$	30,997		35.0	%
(Decrease) increase in income taxes resulting from:
Tax-exempt interest income	(1,197		)	(1.2	)	(1,235		)	(1.4	)	(1,152		)	(1.3	)
State taxes, net of federal income tax benefit	2,627			2.6		2,165			2.4		2,215			2.5
Deferred tax liability remeasurement	(2,614		)	(2.6	)	—			—		—			—
Other	(983		)	(0.9	)	(784		)	(0.8	)	(983		)	(1.1	)
Total	$	33,309		32.9	%	$	31,340		35.2	%	$	31,077		35.1	%

Schedule of deferred tax assets and liabilities

The following table shows the composition of deferred tax assets and liabilities as of December 31, 2017 and 2016.

(Dollars in thousands)	2017			2016
Deferred tax assets:
Reserve for loan and lease losses	$	23,791		$	34,663
Accruals for employee benefits	2,369			3,948
Tax advantaged partnerships	—			1,411
Net unrealized losses on securities available-for-sale	1,285			—
Other	622			477
Total deferred tax assets	28,067			40,499
Deferred tax liabilities:
Differing depreciable bases in premises and leased equipment	22,641			31,449
Net unrealized gains on securities available-for-sale	—			807
Differing bases in assets related to acquisitions	3,954			6,170
Tax advantaged partnerships	1,921			—
Mortgage servicing	745			1,540
Capitalized loan costs	867			1,463
Prepaid expenses	387			646
Other	222			419
Total deferred tax liabilities	30,737			42,494
Net deferred tax liability	$	(2,670	)	$	(1,995	)

Schedule of reconciliation of the beginning and ending amounts of unrecognized tax benefits

The following table shows a reconciliation of the beginning and ending amounts of unrecognized tax benefits.

(Dollars in thousands)	2017		2016		2015
Balance, beginning of year	$	762	$	380	$	—
Additions based on tax positions related to the current year	350		382		380
Additions for tax positions of prior years	—		—		—
Reductions for tax positions of prior years	—		—		—
Reductions due to lapse in statute of limitations	—		—		—
Settlements	—		—		—
Balance, end of year	$	1,112	$	762	$	380