OTHER ASSETS

Other assets at December 31, 2014 and 2013 consisted of the following (in thousands):



	2014		2013
Deferred debt issuance costs	$	27,204	$	16,465
Security deposits	12,368		10,617
Deferred tax assets	8,548		7,055
Other	9,228		6,432
Total	$	57,348	$	40,569

Deferred debt issuance costs arose from (i) the $1.0 billion aggregate principal amount of 1.0% Convertible Senior Notes, due March 15, 2018, issued in March 2012; (ii) a $1.0 billion revolving credit facility entered into in October 2011; (iii) the $575.0 million aggregate principal amount of 1.25% Convertible Senior Notes, due March 15, 2015, issued in March 2010; (iv) the $1.0 billion aggregate principal amount of 0.35% Convertible Senior Notes, due June 15, 2020, issued in May 2013; (v) the $1.0 billion aggregate principal amount of 0.9% Convertible Senior Notes, due September 15, 2021, issued in August 2014; and (vi) the 1.0 billion Euro aggregate principal amount of 2.375% Senior Notes, due September 23, 2024, issued in September 2014. Deferred debt issuance costs are being amortized using the effective interest rate method and the period of amortization was determined at inception of the related debt agreements based upon the stated maturity dates. Unamortized debt issuance costs written off to interest expense in the years ended December 31, 2014 and 2013 related to early conversion of convertible debt and amounted to $0.5 million and $2.4 million, respectively.