Income Taxes (Tables)
 12 Months Ended
Dec. 31, 2015
Income Tax Disclosure [Abstract]  
Schedule of Components of Income Tax Expense (Benefit)
The provision for income taxes consisted of the following:

 
For the years ended
(dollars in thousands)
December 31,
2015
 
December 31,
2014
 
December 31,
2013
Current tax provision:
 
 
 
 
 
Federal
$
60,837

 
$
39,576

 
$
40,127

State
7,164

 
8,947

 
4,060

Total current provision
68,001

 
48,523

 
44,187

 
 
 
 
 
 
Deferred tax provision:
 
 
 
 
 
Federal
(9,855
)
 
16,037

 
(520
)
State
(2,216
)
 
(1,202
)
 
290

Total deferred (benefit) provision
(12,071
)
 
14,835

 
(230
)
Total provision
$
55,930

 
$
63,358

 
$
43,957
Schedule of Income (Loss) before Income Tax, Domestic and Foreign

Components of income (loss) before income taxes are as follows:

 
For the years ended
 
December 31,
2015
 
December 31,
2014
 
December 31,
2013
 
 
 
 
 
 
United States
$
147,427

 
$
165,289

 
$
122,193

Foreign
(2,109
)
 
—

 
—

Total income before income taxes
$
145,318

 
$
165,289

 
$
122,193
Schedule of Effective Income Tax Rate Reconciliation
A reconciliation of the federal statutory rate to our effective rate is as follows:

 
For the years ended
 
December 31,
2015
 
December 31,
2014
 
December 31,
2013
 
 
 
 
 
 
Federal statutory income tax rate
35.0
 %
 
35.0
 %
 
35.0
 %
State income taxes, net of federal income tax benefit
2.5

 
2.1

 
2.2

Non-deductible expenses
2.0

 
0.3

 
0.3

Domestic manufacturing deduction
(1.3
)
 
—

 
—

Unrecognized tax benefits
0.8

 
1.3

 
(1.0
)
Valuation allowance
0.5

 
—

 
—

Other
(1.0
)
 
(0.4
)
 
(0.5
)
Total
38.5
 %
 
38.3
 %
 
36.0
 %
Summary of Unrecognized Tax Benefits
The following is a reconciliation of the beginning and ending amount of unrecognized tax benefits (which excludes federal benefits of state taxes, interest, and penalties):

(dollars in thousands)
 
Balance at December 31, 2012
$
—

Increases in uncertain tax benefits as a result of tax positions taken in a prior year
2,924

Increases in uncertain tax benefits as a result of tax positions taken in the current year
1,959

Balance at December 31, 2013
4,883

Increases in uncertain tax benefits as a result of tax positions taken in a prior year
206

Increases in uncertain tax benefits as a result of tax positions taken in the current year
2,429

Balance at December 31, 2014
7,518

Increases in uncertain tax benefits as a result of tax positions taken in the current year
1,845

Decreases in uncertain tax benefits from a lapse of applicable statute of limitations
(156
)
Balance at December 31, 2015
$
9,207
Schedule of Deferred Tax Assets and Liabilities
Components of deferred tax assets and liabilities were as follows:
(dollars in thousands)
December 31,
2015
 
December 31,
2014
Deferred tax assets:
 
Inventories
$
1,228

 
$
1,869

Accrued liabilities
12,491

 
307

Transaction costs
—

 
1,085

Stock-based compensation
1,378

 
1,024

Capitalized debt
237

 
301

Long-term incentive plan
834

 
746

Research and development
—

 
41

State net operating loss carryforwards
2,152

 
2,072

Foreign net operating loss carryforwards
254

 
—

State tax credits
1,826

 
325

Federal benefit related to uncertain tax positions
2,697

 
—

Other
518

 
322

Deferred tax assets, gross
23,615

 
8,092

Valuation allowance
(782
)
 
—

Total deferred tax assets, net
22,833

 
8,092

 
 
 
 
Deferred tax liabilities:
 
 
 
Property, plant, and equipment
(20,441
)
 
(18,176
)
Prepaids
(696
)
 
—

Bond premiums
(1,057
)
 
(1,348
)
Total deferred tax liabilities
(22,194
)
 
(19,524
)
 
 
 
 
          Net deferred tax assets (liabilities)
$
639

 
$
(11,432
)