The components of the income tax provision are as follows:



Year Ended December 31, (Dollars in millions)	2018			2017		2016
Current expense:
Federal	$	629		$	539	$	959
State	151			80		97
Total current expense	780			619		1,056
Deferred expense:
Federal	26			253		(14		)
State	(3		)	39		16
Total deferred expense	23			292		2
Provision for income taxes	$	803		$	911	$	1,058

The reasons for the difference between the provision for income taxes and the amount computed by applying the statutory Federal income tax rate to income before income taxes were as follows:



Year Ended December 31, (Dollars in millions)	2018			2017			2016
Federal income taxes at statutory rate	$	853		$	1,164		$	1,225
Increase (decrease) in provision for income taxes as a result of:
State income taxes, net of federal tax benefit	117			77			73
Affordable housing projects proportional amortization	260			236			205
Affordable housing projects tax credits and other tax benefits	(317		)	(319		)	(279		)
Tax-exempt income	(90		)	(139		)	(151		)
Federal tax reform impact	(27		)	(43		)	—
Excess tax benefits for equity-based compensation	(17		)	(52		)	—
Other, net	24			(13		)	(15		)
Provision for income taxes	$	803		$	911		$	1,058
Effective income tax rate	19.8		%	27.4		%	30.2		%
Statutory federal tax rate	21.0		%	35.0		%	35.0		%

The Tax Cuts and Jobs Act was signed into law on December 22, 2017. Amounts reflected in the above table as Federal tax reform impact for 2018 relate to the revaluation of deferred taxes on positions taken in the 2017 tax return filing, while amounts for 2017 relate to the net tax benefit recognized as a result of the revaluation of deferred taxes and investments in affordable housing projects.

The tax effects of temporary differences that gave rise to deferred tax assets and liabilities are reflected in the table below:



December 31, (Dollars in millions)	2018			2017
Deferred tax assets:
ALLL	$	374		$	359
Postretirement plans	360			311
Net unrealized loss on AFS securities	156			112
Equity-based compensation	82			66
Reserves and expense accruals	203			114
Partnerships	77			70
Other	158			160
Total deferred tax assets	1,410			1,192
Deferred tax liabilities:
Prepaid pension plan expense	453			436
MSRs	248			234
Lease financing	376			366
Loan fees and expenses	169			114
Identifiable intangible assets	183			163
Other	82			31
Total deferred tax liabilities	1,511			1,344
Net deferred tax asset (liability)	$	(101	)	$	(152	)

On a periodic basis, BB&T evaluates its income tax positions based on tax laws and regulations and financial reporting considerations, and records adjustments as appropriate. This evaluation takes into consideration the status of current taxing authorities' examinations of BB&T's tax returns, recent positions taken by the taxing authorities on similar transactions and the overall tax environment in relation to tax-advantaged transactions. The amounts of unrecognized tax benefits and accrued tax-related interest penalties were immaterial at December 31, 2018, 2017 and 2016. Further, the amount of net interest and penalties related to unrecognized tax benefits was immaterial for all periods presented.

The Company's federal income tax returns are no longer subject to examination by the IRS for taxable years prior to 2015. With limited exceptions, the Company is no longer subject to examination by state and local taxing authorities for taxable years prior to 2014.