LONG-TERM BORROWINGS AND SUBORDINATED DEBT

Long-term borrowings are for original terms greater than or equal to one year and are comprised of FHLB advances and junior subordinated debt securities. Our long-term borrowings at the Pittsburgh FHLB were $47.2 million as of December 31, 2017 and $14.7 million as of December 31, 2016. FHLB borrowings are secured by a blanket lien on residential mortgages and other real estate secured loans. Total loans pledged as collateral at the FHLB were $3.5 billion at December 31, 2017. We were eligible to borrow up to an additional $1.8 billion based on qualifying collateral, to a maximum borrowing capacity of $2.5 billion at December 31, 2017.

The following table represents the balance of long-term borrowings, the weighted average interest rate as of December 31 and interest expense for the years ended December 31:



(dollars in thousand)	2017			2016			2015
Long-term borrowings	$	47,301		$	14,713		$	117,043
Weighted average interest rate	1.88		%	2.91		%	0.81		%
Interest expense	$	463		$	670		$	790

Scheduled annual maturities and average interest rates for all of our long-term debt for each of the five years subsequent to December 31, 2017 and thereafter are as follows:



(dollars in thousands)	Balance		Average Rate
2018	$	2,496	3.60	%
2019	37,514		1.60	%
2020	2,004		3.22	%
2021	1,057		3.44	%
2022	529		4.50	%
Thereafter	3,701		1.96	%
Total	$	47,301	1.88	%

Junior Subordinated Debt Securities

The following table represents the composition of junior subordinated debt securities at December 31 and the interest expense for the years ended December 31:



	2017				2016				2015
(dollars in thousands)	Balance		Interest Expense		Balance		Interest Expense		Balance		Interest Expense
2006 Junior subordinated debt	$	25,000	$	708	$	25,000	$	580	$	25,000	$	554
2008 Junior subordinated debt—trust preferred securities	20,619		955		20,619		854		20,619		773
Total	$	45,619	$	1,663	$	45,619	$	1,434	$	45,619	$	1,327

The following table summarizes the key terms of our junior subordinated debt securities:



(dollars in thousands)	2006 Junior Subordinated Debt	2008 Trust Preferred Securities
Junior Subordinated Debt	$25,000	—
Trust Preferred Securities	—	$20,619
Stated Maturity Date	12/15/2036	3/15/2038
Optional redemption date at par	Any time after 9/15/2011	Any time after 3/15/2013
Regulatory Capital	Tier 2	Tier 1
Interest Rate	3 month LIBOR plus 160 bps	3 month LIBOR plus 350 bps
Interest Rate at December 31, 2017	2.92%	4.82%

NOTE 16. LONG-TERM BORROWINGS AND SUBORDINATED DEBT - continued

We completed a private placement of the trust preferred securities to a financial institution during the first quarter of 2008. As a result, we own 100 percent of the common equity of STBA Capital Trust I. The trust was formed to issue mandatorily redeemable capital securities to third-party investors. The proceeds from the sale of the securities and the issuance of the common equity by STBA Capital Trust I were invested in junior subordinated debt securities issued by us. The third party investors are considered the primary beneficiaries of STBA Capital Trust I; therefore, the trust qualifies as a VIE, but is not consolidated into our financial statements. STBA Capital Trust I pays dividends on the securities at the same rate as the interest paid by us on the junior subordinated debt held by STBA Capital Trust I.