Common Stock Warrant Liability

3 Months Ended

Mar. 31, 2014

Common Stock Warrant Liability

NOTE 7 — COMMON STOCK WARRANT LIABILITY

In June 2010, Signature issued warrants to purchase an aggregate of 1.5 million shares of the Company’s common stock (the “Warrants”). The aggregate purchase price for the Warrants was $0.3 million, due in equal installments as the Warrants vest. The Warrants vested 20% upon issuance and, thereafter, vest 20% annually on the anniversary of the issuance date. As of March 31, 2014, the Warrants are 80% vested and the Company has received $0.2 million of the aggregate purchase price. The Warrants expire in June 2020 and had an original exercise price of $10.30 per share. The Warrants were issued without registration in reliance on the exemption set forth in Section 4(2) of the Securities Act of 1933, as amended.

The Warrants include customary terms that provide for certain adjustments of the exercise price and the number of shares of common stock to be issued upon the exercise of the Warrants in the event of stock splits, stock dividends, pro rata distributions and certain other fundamental transactions. Additionally, the Warrants are subject to pricing protection provisions. During the term of the Warrants, the pricing protection provisions provide that certain issuances of new shares of common stock at prices below the current exercise price of the Warrants automatically reduce the exercise price of the Warrants to the lowest per share purchase price of common stock issued.

In October 2010, January 2011, and April 2011, restricted common stock was issued to nonexecutive members of the Board under the Company’s director compensation program (the “Director Compensation Program”) that each triggered the pricing protection provisions of the Warrants. The restricted common stock issued to nonexecutive members of the Board in April 2011 reduced the exercise price of the Warrants to $6.90 per share, the grant date fair value of the restricted common stock issued. In July 2011, the Company issued approximately 0.3 million shares of common stock as purchase consideration in the NABCO business combination. The NABCO business combination common stock was issued at $6.64 per share, thereby reducing the exercise price of the Warrants to $6.64 per share; however, the holders of approximately 79.3% of the Warrants waived the pricing protection provisions related to shares issued in the NABCO business combination and the exercise price related to those Warrants remains at $6.90 per share.

The Company utilizes a trinomial lattice option pricing model to estimate the fair value of the common stock warrant liability. A decrease in the common stock warrant liability results in other income, while an increase in the common stock warrant liability results in other expense. The following table presents changes in fair value of common stock warrant liability during the three months ended March 31, 2014 and 2013:

	Three Months Ended March 31,
(Dollars in thousands)	2014			2013
Beginning balance	$	9,300		$	2,350
Change in fair value of common stock warrant liability		(800	)		1,450
Ending balance	$	8,500		$	3,800

See Note 11— Fair Value Measurements for additional information on the assumptions used to estimate the fair value of common stock warrant liability.