Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

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)	2016		2015		2014
Current:
Federal	$	25,479	$	26,092	$	20,999
State	3,005		3,365		1,034
Total current	28,484		29,457		22,033
Deferred:
Federal	2,530		1,577		4,022
State	326		43		319
Total deferred	2,856		1,620		4,341
Total provision	$	31,340	$	31,077	$	26,374

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.

	2016					2015					2014
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	$	31,194		35.0	%	$	30,997		35.0	%	$	29,555		35.0	%
(Decrease) increase in income taxes resulting from:
Tax-exempt interest income	(1,235		)	(1.4	)	(1,152		)	(1.3	)	(1,236		)	(1.5	)
State taxes, net of federal income tax benefit	2,165			2.4		2,215			2.5		2,300			2.7
Reduction in uncertain tax positions	—			—		—			—		(3,300		)	(3.9	)
Other	(784		)	(0.8	)	(983		)	(1.1	)	(945		)	(1.1	)
Total	$	31,340		35.2	%	$	31,077		35.1	%	$	26,374		31.2	%

Schedule of deferred tax assets and liabilities

The following table shows the composition of deferred tax assets and liabilities as of December 31, 2016 and 2015.

(Dollars in thousands)	2016			2015
Deferred tax assets:
Reserve for loan and lease losses	$	34,663		$	34,410
Accruals for employee benefits	3,948			3,816
Tax advantaged partnerships	1,411			307
Other	477			598
Total deferred tax assets	40,499			39,131
Deferred tax liabilities:
Differing depreciable bases in premises and leased equipment	31,449			27,274
Net unrealized gains on securities available-for-sale	807			3,940
Differing bases in assets related to acquisitions	6,170			5,738
Mortgage servicing	1,540			1,630
Capitalized loan costs	1,463			1,454
Prepaid expenses	646			1,055
Other	419			312
Total deferred tax liabilities	42,494			41,403
Net deferred tax liability	$	(1,995	)	$	(2,272	)

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)	2016		2015		2014
Balance, beginning of year	$	380	$	—	$	4,611
Additions based on tax positions related to the current year	382		380		66
Additions for tax positions of prior years	—		—		592
Reductions for tax positions of prior years	—		—		(553		)
Reductions due to lapse in statute of limitations	—		—		(1,650		)
Settlements	—		—		(3,066		)
Balance, end of year	$	762	$	380	$	—