INCOME TAXES

The Company's provision for income taxes in interim periods is based on an estimated annual effective income tax rate derived, in part, from estimated annual pre-tax results from ordinary operations. The annual effective income tax rate is reviewed and, if necessary, adjusted on a quarterly basis.

The Company's income tax expense consisted of the following:



	Three Months Ended					Nine Months Ended
	September 30,					September 30,
	2016			2015		2016			2015
Income before provision for income taxes	$	39,023		$	29,804	$	121,119		$	94,774
Income tax expense using estimated annual effective income tax rate	15,306			11,743		47,474			37,426
Changes in effective tax rates	(1,149		)	1,539		—			—
Impact of discrete items, net	(841		)	412		(792		)	313
Income tax expense	$	13,316		$	13,694	$	46,682		$	37,739

The discrete items for the nine months ended September 30, 2016 are primarily related to the results of recent state income tax audits and a change in the marginal state tax rate as a result of recent state legislation changes. The discrete items for the nine months ended September 30, 2015 are primarily related to the rate differential in other comprehensive income and the results of a recent state income tax audit.