Shareholders' Equity (Tables)

During the years ended December 31, 2013 and 2012, the changes in accumulated other comprehensive loss, presented net of tax, were as follows (in millions):

	Year ended December 31, 2013											Year ended December 31, 2012
	Defined benefit pension plans			Derivative instruments			Marketable securities		Total			Defined benefit pension plans			Derivative instruments			Marketable securities			Total
Balance, beginning of period	$	(511	)	$	(10	)	$	—	$	(521	)	$	(501	)	$	7		$	(2	)	$	(496	)
Other comprehensive income (loss) before reclassifications		202			(6	)		—		196			(52	)		1			—			(51	)
Reclassifications to net income		45			18			—		63			42			(1	)		2			43
Other comprehensive income (loss), net		247			12			—		259			(10	)		—			2			(8	)
Reclassification from redeemable noncontrolling interest		—			—			—		—			—			(17	)		—			(17	)
Balance, end of period	$	(264	)	$	2		$	—	$	(262	)	$	(511	)	$	(10	)	$	—		$	(521	)

Significant reclassifications from accumulated other comprehensive income to net income included the following (in millions):

		Years ended December 31,
	Statement of operations classification	2013			2012			2011
Defined benefit pension plans
Actuarial losses		$	48		$	45		$	26
Prior service costs			—			(1	)		(1	)
Settlements and curtailments			1			3			—
Total amortization, before income taxes	Net periodic benefit costs (a)		49			47			25
Income tax (benefit) expense	Income tax expense		(4	)		(5	)		13
Total amortization, net of income taxes		$	45		$	42		$	38

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(a)

We recognize the amortization of accumulated other comprehensive income components related to defined benefit pension plans in net periodic benefit costs. In the year ended December 31, 2013, the amortization components of our net periodic benefit costs were $37 million, recorded in operating and maintenance costs, and $12 million, recorded in general and administrative costs. In the year ended December 31, 2012, the amortization components of our net periodic benefit costs were $31 million, recorded in operating and maintenance costs, and $16 million, recorded in general and administrative costs. In the year ended December 31, 2011, the amortization components of our net periodic benefit costs were $17 million, recorded in operating and maintenance costs, and $8 million, recorded in general and administrative costs. See Note 14—Postemployment Benefit Plans.