Three months ended September 30

Nine months ended September 30

Pension benefits

Other benefits

Pension benefits

Other benefits

(in thousands)

2011

2010

2011

2010

2011

2010

2011

2010

Service cost

$

8,525

$

7,376

$

868

$

1,248

$

26,266

$

21,424

$

3,308

$

3,539

Interest cost

16,137

16,197

2,273

2,565

48,717

48,330

7,151

7,901

Expected return on plan assets

(17,400

)

(17,272

)

(2,687

)

(2,792

)

(51,673

)

(51,687

)

(7,992

)

(8,310

)

Amortization of unrecognized transition obligation

1

—

2

—

Amortization of prior service gain

(98

)

(97

)

(587

)

(83

)

(292

)

(291

)

(1,120

)

(187

)

Recognized actuarial loss (gain)

4,005

1,942

115

(5

)

12,724

5,449

170

(8

)

Net periodic benefit cost

11,170

8,147

(18

)

933

35,744

23,227

1,517

2,935

Impact of PUC D&Os

(713

)

2,574

327

1,512

(2,813

)

7,602

3,079

4,133

Net periodic benefit cost (adjusted for impact of PUC D&Os)

$

10,457

$

10,721

$

309

$

2,445

$

32,931

$

30,829

$

4,596

$

7,068