5. Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Income Tax Expense

	Year ended December 31,
	2015			2014			2013
Current  —  Federal	$	11,848		$	12,626		$	12,541
—  State		1,528			1,585			1,065
		13,376			14,211			13,606
Deferred  —  Federal		(1,364	)		31			(1,063	)
— State		(67	)		(29	)		140
		(1,431	)		2			(923	)
Total income tax expense	$	11,945		$	14,213		$	12,683

Deferred Income Tax Assets and Liabilities with Temporary Differences and Carryforwards

	2015		2014
Deferred tax assets:
Benefit plans	$	1,958	$	1,535
Inventories		473		483
Other		733		158
Total deferred tax assets	$	3,164	$	2,176
Deferred tax liabilities:
Property, plant and equipment	$	9,585	$	9,648
Patents and goodwill		2,897		2,926
Other		91		158
Total deferred tax liabilities	$	12,573	$	12,732
Net deferred tax liability	$	9,409	$	10,556
Balance Sheet classification:
Non-current deferred income tax liability	$	9,989	$	11,129
Current deferred income tax asset		580		573
Net deferred tax liability	$	9,409	$	10,556

Illustration of Total Income Tax Expense Difference with Amount Provided by Applying Statutory Federal Income Tax Rate to Pretax Earnings

	Year ended December 31,
	2015			2014			2013
Income tax expense at the statutory federal income tax rate	$	14,304		$	14,707		$	13,743
Increase (decrease) resulting from:
State income taxes		882			934			770
Section 199 manufacturing deduction		(1,383	)		(1,290	)		(1,307	)
R&D tax credits		(2,254	)		(393	)		(626	)
Other, net		396			255			103
Total income tax expense	$	11,945		$	14,213		$	12,683

Reconciliation of Beginning and Ending Balances of Total Amounts of Gross Unrecognized Tax Benefits

Gross unrecognized tax benefits at January 1, 2013	$	541
Increase in tax positions for prior years		11
Increase in tax positions for current year		0
Lapse in statutes of limitation		(206	)
Gross unrecognized tax benefits at December 31, 2013	$	346
Increase in tax positions for prior years		6
Increase in tax positions for current year		0
Lapse in statutes of limitation		(223	)
Gross unrecognized tax benefits at December 31, 2014	$	129
Increase in tax positions for prior years		122
Increase in tax positions for current year		0
Lapse in statutes of limitation		(131	)
Gross unrecognized tax benefits at December 31, 2015	$	120