10. Interest Costs

We capitalize a portion of our interest on funds borrowed during the active construction period of major capital projects. Capitalized interest is added to the cost of the underlying asset and amortized over the useful lives of the assets. We commenced capitalizing interest on major capital projects when we entered into the Senior Term Facility on June 21, 2012.

The following is a summary of our interest costs for the years ended December 31, 2013, 2012 and 2011 (in thousands):


	For the Years Ended December 31,
	2013		2012		2011
Interest expense	$	23,458	$	8,109	$	280
Amortization of deferred financing costs		2,832		804		—
Non lender fees ⁽¹⁾		2,982		—		—

Interest costs charged to expense		29,272		8,913		280
Interest costs capitalized to property and equipment		872		200		—
Interest costs capitalized to software		671		129		—

Total interest costs	$	30,815	$	9,242	$	280

(1)

Primarily consists of fees paid to legal counsel and underwriters in connection with the New Borrowing.