11. Income Taxes:

The components of the income tax provision are as follows (in thousands):


	December 31,
	2016		2015		2014
Federal:
Current	$	166,758	$	168,596	$	167,745
Deferred		15,596		12,866		2,262

		182,354		181,462		170,007

State:
Current		4,296		20,948		21,109
Deferred		2,553		1,628		297

		6,849		22,576		21,406

Total	$	189,203	$	204,038	$	191,413

The Company files its tax return on a consolidated basis with its subsidiaries. The remaining affiliated professional contractors file tax returns on an individual basis.

The effective tax rate was 36.80%, 37.76% and 37.63% for the years ended December 31, 2016, 2015 and 2014, respectively. During the three months ended September 30, 2016, the Company settled a certain tax matter with a taxing authority. In connection with this settlement, the Company’s effective income tax rate was favorably impacted by $10.6 million. After excluding this favorable impact, the effective tax rate for December 31, 2016 was 38.87%, as compared to 37.76% for 2015. The increase primarily relates to non-recurring discrete items that occurred in 2015 and an increase in the valuation allowance on deferred tax assets in 2016.

The differences between the effective rate and the United States federal income tax statutory rate are as follows:


	December 31,
	2016			2015			2014
Tax at statutory rate		35.00	%		35.00	%		35.00	%
State income tax, net of federal benefit		2.94			2.97			2.74
Non-deductible expenses		0.43			0.34			0.33
Change in accrual estimates relating to uncertain tax positions		(2.11	)		(0.43	)		(0.59	)
Change in valuation allowance		0.48			0.29			—
Other, net		0.06			(0.41	)		0.15

Income tax provision		36.80	%		37.76	%		37.63	%

All of the Company’s deferred tax assets and liabilities are classified as long-term. The significant components of deferred income tax assets and liabilities are as follows (in thousands):


	December 31,
	2016			2015
Allowance for uncollectible accounts	$	103,525		$	82,928
Reserves and accruals		62,212			66,655
Stock-based compensation		13,726			13,662
Net operating loss carryforward		49,156			51,505
Property and equipment		1,621			3,116
Other		1,610			2,723

Deferred tax assets before valuation allowance		231,850			220,589
Less: Valuation allowance		(4,014	)		(1,552	)

Deferred tax assets, net of valuation allowance		227,836			219,037

Gross deferred tax liabilities:
Amortization		(380,594	)		(311,303	)
Accrual to cash adjustment		(53,771	)		(55,046	)
Other		(1,023	)		(6,693	)

Total deferred tax liabilities		(435,388	)		(373,042	)

Net deferred tax liability	$	(207,552	)	$	(154,005	)

The income tax benefit related to the exercise of stock options, the vesting of restricted and deferred stock and the purchase of shares under the Company’s non-qualified employee stock purchase plan in excess of amounts recorded as equity compensation expense reduces taxes currently payable and is credited to additional paid-in capital. Such amounts totaled $4.2 million, $11.6 million and $17.5 million for the years ended December 31, 2016, 2015 and 2014, respectively.

The Company has net operating loss carryforwards for federal and state tax purposes totaling $130.0 million, $136.6 million, and $29.0 million at December 31, 2016, 2015 and 2014, respectively, expiring at various times in 2019 through 2036. The change in net operating loss carryforwards in 2015 as compared to 2014 was primarily due to timing differences related to the recognition of income for tax purposes associated with acquisitions.

As of December 31, 2016, 2015 and 2014, the Company’s liability for uncertain tax positions, excluding accrued interest and penalties, was $9.5 million, $18.4 million and $17.2 million, respectively. As of December 31, 2016, the Company had $9.5 million of uncertain tax positions that, if recognized, would favorably impact its effective tax rate.

The following table summarizes the activity related to the Company’s liability for uncertain tax positions for the years ended December 31, 2016, 2015 and 2014 (in thousands):


	Years Ended December 31,
	2016			2015			2014
Balance at beginning of year	$	18,447		$	17,165		$	14,902
Increases related to prior year tax positions		301			467			40
Decreases related to prior year tax positions		(3,927	)		(1,168	)		—
Increases related to current year tax positions		2,258			3,675			3,750
Settlements		(5,644	)		—			—
Decreases related to lapse of statutes of limitations		(1,966	)		(1,692	)		(1,527	)

Balance at end of year	$	9,469		$	18,447		$	17,165

During the year ended December 31, 2016, the Company decreased its liability for uncertain tax positions by a total of $9.0 million, primarily related to the settlement of a certain tax matter with a taxing authority and the expiration of statutes of limitation, partially offset by additional taxes on current year positions. During the year ended December 31, 2015, the Company increased its liability for uncertain tax positions by $1.2 million, primarily related to additional taxes on current year positions, partially offset by decreases due to the expiration of statutes of limitation and current year tax positions.

In addition, the Company anticipates that its liability for uncertain tax positions will be increased by $2.2 million for additional taxes and decreased by $2.1 million related to the expiration of certain statutes of limitation over the next 12 months.

The Company includes interest and penalties related to income tax liabilities in income tax expense. The Company recognized an income tax benefit of $7.9 million and income tax expense of $0.6 million and $0.3 million related to interest and penalties during the years ended December 31, 2016, 2015 and 2014, respectively. The 2016 benefit was primarily related to the settlement of the tax matter discussed above. At December 31, 2016 and 2015, the Company’s accrued liability for interest and penalties related to income tax liabilities totaled $1.4 million and $9.3 million, respectively.

The Company is currently subject to U.S. Federal and various state income tax examinations for the tax years 2012 through 2015.