RETIREMENT BENEFITS

The cost to the company of its retirement benefit plans is shown in the following table:



	Three Months Ended September 30												Nine Months Ended September 30
	Pension Benefits						Medical and Life Benefits						Pension Benefits						Medical and Life Benefits
$ in millions	2013			2012			2013			2012			2013			2012			2013			2012
Components of net periodic benefit cost
Service cost		$129			$131			$ 9			$ 8			$ 387			$ 392			$27			$25
Interest cost	279			296			24			28			838			888			72			82
Expected return on plan assets	(452		)	(427		)	(19		)	(17		)	(1,357		)	(1,281		)	(57		)	(51		)
Amortization of:
Prior service credit	(15		)	(15		)	(13		)	(13		)	(44		)	(44		)	(38		)	(38		)
Net loss from previous years	152			107			8			5			456			321			23			15
Other	—			—			—			—			—			2			—			—
Net periodic benefit cost		$ 93			$ 92			$ 9			$ 11			$ 280			$ 278			$27			$33

Employer Contributions

The company’s required minimum funding in 2013 for its defined benefit pension plans and its post-retirement benefit plans is approximately $66 million and $110 million, respectively. For the nine months ended September 30, 2013, contributions of $561 million have been made to the company’s defined benefit pension plans, including a voluntary contribution of $500 million in April 2013, and contributions of $87 million have been made to the company’s post-retirement benefit plans.

The company also sponsors defined contribution plans. For the three months ended September 30, 2013 and 2012, contributions of $63 million and $66 million, respectively, were made to these plans. For the nine months ended September 30, 2013 and 2012, contributions of $213 million and $218 million, respectively, were made to these plans.