11. Income Taxes:

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


	December 31,
	2014		2013		2012
Federal:
Current	$	167,745	$	134,938	$	111,940
Deferred		2,262		14,784		19,814

		170,007		149,722		131,754

State:
Current		21,109		17,037		13,980
Deferred		297		1,136		1,530

		21,406		18,173		15,510

Total	$	191,413	$	167,895	$	147,264

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 37.63%, 37.44% and 37.94% for the years ended December 31, 2014, 2013 and 2012, respectively.

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


	December 31,
	2014			2013			2012
Tax at statutory rate		35.00	%		35.00	%		35.00	%
State income tax, net of federal benefit		2.74			2.63			2.60
Non-deductible expenses		0.33			0.27			0.36
Change in accrual estimates relating to uncertain tax positions		(0.59	)		(0.48	)		(0.15	)
Other, net		0.15			0.02			0.13

Income tax provision		37.63	%		37.44	%		37.94	%

The significant components of deferred income tax assets and liabilities are as follows (in thousands):


	December 31, 2014									December 31, 2013
	Total			Current			Non- Current			Total			Current			Non- Current
Allowance for uncollectible accounts	$	48,178		$	48,178		$	—		$	42,425		$	42,425		$	—
Reserves and accruals		62,708			26,066			36,642			52,519			18,341			34,178
Stock-based compensation		14,354			8,346			6,008			16,457			3,628			12,829
Net operating loss carryforward		10,933			1,504			9,429			6,385			3,744			2,641
Property and equipment		1,524			—			1,524			1,310			—			1,310
Other		1,461			583			878			446			446			—

Total deferred tax assets		139,158			84,677			54,481			119,542			68,584			50,958

Amortization		(214,968	)		—			(214,968	)		(162,399	)		—			(162,399	)
Accrual to cash adjustment		(38,524	)		(38,524	)		—			(37,818	)		(37,818	)		—
Other		(192	)		(192	)		—			—			—			—

Total deferred tax liabilities		(253,684	)		(38,716	)		(214,968	)		(200,217	)		(37,818	)		(162,399	)

Net deferred tax (liability) asset	$	(114,526	)	$	45,961		$	(160,487	)	$	(80,675	)	$	30,766		$	(111,441	)

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 approximately $17.5 million, $19.0 million, and $6.2 million for the years ended December 31, 2014, 2013 and 2012, respectively.

The Company has net operating loss carryforwards for federal and state tax purposes totaling approximately $29.0 million, $16.9 million, and $14.9 million at December 31, 2014, 2013 and 2012, respectively, expiring at various times in 2019 through 2034. The changes in net operating loss carryforwards in 2014 and 2013 are primarily due to timing differences related to the recognition of income for tax purposes associated with physician practice acquisitions.

As of December 31, 2014, 2013 and 2012, the Company’s liability for uncertain tax positions, excluding accrued interest and penalties, was $17.2 million, $14.9 million and $13.1 million, respectively. The Company had approximately $16.1 million of uncertain tax positions that, if recognized, would favorably impact its effective tax rate at December 31, 2014.

The following table summarizes the activity related to the Company’s liability for uncertain tax positions for the years ended December 31, 2014, 2013 and 2012 (in thousands):


	Years Ended December 31,
	2014			2013			2012
Balance at beginning of year	$	14,902		$	13,072		$	16,165
Increases related to prior year tax positions		40			338			102
Decreases related to prior year tax positions		—			(38	)		—
Increases related to current year tax positions		3,750			2,955			2,478
Decreases related to current year tax positions		—			—			(3,671	)
Decreases related to lapse of statutes of limitations		(1,527	)		(1,425	)		(2,002	)

Balance at end of year	$	17,165		$	14,902		$	13,072

During the years ended December 31, 2014 and 2013, the Company increased its liability for uncertain tax positions by a total of $2.3 million and $1.8 million, respectively, primarily related to additional taxes on current year positions, partially offset by decreases due to the expiration of statutes of limitation.

The Company includes interest and penalties related to income tax liabilities in income tax expense. The Company recognized a net increase of $0.3 million related to interest and penalties during the year ended December 31, 2014. The Company recognized a net decrease of $0.6 million and a net increase of $0.3 million, respectively, of interest and penalties related to income tax liabilities during the years ended December 31, 2013 and 2012. At December 31, 2014 and 2013, the Company’s accrued liability for interest and penalties related to income tax liabilities totaled $8.7 million and $8.4 million, respectively.

At December 31, 2014 and 2013, the Company’s total liability for uncertain tax positions of $25.9 million and $23.3 million, respectively, is included in other liabilities as presented in the Company’s Consolidated Balance Sheet.

The Company anticipates that its liability for uncertain tax positions will be increased by approximately $4.9 million for additional taxes and decreased by approximately $1.7 million related to the expiration of certain statutes of limitation over the next 12 months.

The Company is currently subject to U.S. Federal and various state income tax examinations for the tax years 2004 through 2013.