Basic net income per common share is computed by dividing net income, after deducting dividends paid or accrued on preferred stock and allocating earnings to stock awards deemed to be participating securities pursuant to the two-class method, by the average number of shares of common stock outstanding, calculated excluding unvested stock awards. Participating securities include unvested stock awards that contain non-forfeitable rights to dividends prior to vesting.

Diluted net income per common share is computed by dividing the numerator used to compute basic net income per common share by the denominator used to compute basic net income per common share, further adjusted for the dilutive effect, if any, of equity-based awards and shares of preferred stock when and if convertible into shares of common stock. Shares of the Company’s 7.50% Series E Cumulative Redeemable Preferred Stock are contingently convertible into shares of common stock only upon the occurrence of a change in control and therefore are not considered dilutive securities absent such an occurrence. Any unvested stock awards that are deemed participating securities are included in the calculation of diluted net income per common share, if dilutive, under either the two-class method or the treasury stock method, depending upon which method produces the more dilutive result. Components of the computation of basic and diluted net income per common share were as follows for the indicated periods (dollars in thousands, except per share amounts):

	Year ended December 31
	2018			2017			2016
Basic net income per common share
Numerator for basic net income per common share:
Net income	$	50,072		$	79,589		$	82,873
Preferred stock dividends		(19,368	)		(17,442	)		(15,372	)
Earnings participation of unvested stock awards		(102	)		(150	)		(140	)
	$	30,602		$	61,997		$	67,361
Denominator for basic net income per common share:
Average number of shares of common stock outstanding		91,565			96,023			95,957
Average unvested stock awards outstanding		(451	)		(305	)		(301	)
		91,114			95,718			95,656

	$	0.34		$	0.65		$	0.70
Diluted net income per common share
Numerator for diluted net income per common share:
Numerator for basic net income per common share	$	30,602		$	61,997		$	67,361
Denominator for diluted net income per common share:
Denominator for basic net income per common share		91,114			95,718			95,656
Net effect of dilutive equity-based awards		116			125			163
		91,230			95,843			95,819

	$	0.34		$	0.65		$	0.70