Pension Benefit and Retirement Health and Life Insurance Benefits (Tables)

12 Months Ended

Dec. 31, 2012

Compensation and Retirement Disclosure [Abstract]

Change in benefit obligation [Table Text Block]

(Dollars in thousands)	Pension Benefits						Retirement Health and Life Insurance Benefits
Change in benefit obligation:	2012			2011			2012			2011
Benefit obligation at beginning of year	$	193,715		$	157,340		$	10,495		$	9,149
Service cost	4,596			3,922			630			693
Interest cost	8,420			8,535			364			413
Actuarial (gain) loss	16,636			30,616			(395		)	1,117
Benefit payments	(6,800		)	(6,874		)	(795		)	(877		)
Settlement charge	(6,723		)	—			—			—
Special termination benefit	—			176			1,592			—
Benefit obligation at end of year	$	209,844		$	193,715		$	11,891		$	10,495

Change in plan assets [Table Text Block]

Change in plan assets:
Fair value of plan assets at the beginning of the year	$	120,565		$	125,261		$	—		$	—
Actual return on plan assets	13,775			(2,849		)	—			—
Employer contributions	22,723			5,027			795			877
Benefit payments	(6,800		)	(6,874		)	(795		)	(877		)
Settlement charge	(6,723		)	—			—			—
Fair value of plan assets at the end of the year	143,540			120,565			—			—
Funded status	$	(66,304	)	$	(73,150	)	$	(11,891	)	$	(10,495	)

Amounts recognized in consolidated balance sheet [Table Text Block]

Amounts recognized in the consolidated balance sheet consist of:

(Dollars in thousands)	Pension Benefits						Retirement Health and Life Insurance Benefits
	2012			2011			2012			2011
Noncurrent assets	$	—		$	—		$	—		$	—
Current liabilities	(362		)	(4,279		)	(1,237		)	(1,009		)
Noncurrent liabilities	(65,942		)	(68,871		)	(10,654		)	(9,486		)
Net amount recognized at end of year	$	(66,304	)	$	(73,150	)	$	(11,891	)	$	(10,495	)

Schedule of net periodic benefit cost not yet recognized [Table Text Block]

(Dollars in thousands)	Pension Benefits		Retirement Health and Life Insurance Benefits
	2012		2012
Net actuarial loss	$	87,911	$	3,187
Prior service cost	1,660		(229		)
Net amount recognized at end of year	$	89,571	$	2,958

Components of net periodic benefit cost [Table Text Block]

(Dollars in thousands)	Pension Benefits									Postretirement Health and Life Insurance Benefits
	2012			2011			2010			2012			2011			2010
Service cost	$	4,596		$	3,922		$	3,563		$	630		$	693		$	661
Interest cost	8,420			8,535			8,345			364			413			398
Expected return of plan assets	(9,892		)	(10,559		)	(9,628		)	—			—			—
Amortization of prior service cost	463			597			600			(451		)	(627		)	(626		)
Amortization of net loss	5,471			2,331			1,824			313			421			329
Settlement charge/(credit)	2,073			—			372			—			—			—
Special termination benefit	—			176			—			1,592			—			—
Net periodic benefit cost	$	11,131		$	5,002		$	5,076		$	2,448		$	900		$	762

Schedule of assumptions used [Table Text Block]

Weighted-average assumptions used to determine benefit obligations at December 31:

	Pension Benefits				Retirement Health and Life Insurance Benefits
	2012		2011		2012		2011
Discount rate	4.00	%	4.50	%	2.50	%	3.50	%
Rate of compensation increase	4.00	%	4.00	%	—		—
Expected long-term rate of return on plan assets	7.50	%	7.75	%	—		—

Weighted-average assumptions used to determine net benefit cost for the years ended:

	Pension Benefits				Retirement Health and Life Insurance Benefits
	2012		2011		2012		2011
Discount rate	4.50	%	5.50	%	3.50	%	4.50	%
Expected long-term rate of return on plan assets	7.75	%	8.50	%	—		—
Rate of compensation increase	4.00	%	4.00	%	—		—

Schedule of effect of one-percentage-point change in assumed health care cost trend rates [Table Text Block]

A one-percentage point change in assumed health care cost trend rates would have the following effects:

(Dollars in thousands)	One Percentage Point
	Increase		Decrease
Effect on total service and interest cost	$	82	$	(70	)
Effect on other postretirement benefit obligations	695		(647		)

Schedule of allocation of plan assets [Table Text Block]

The following table presents the fair value of the net assets by asset category at December 31, 2012 and 2011:

(Dollars in thousands)	2012		2011
Pooled separate accounts	$	29,869	$	32,072
Mutual funds	98,269		47,255
Common stock	—		27,804
Guaranteed deposit account	15,402		13,266
Interest bearing cash	—		168
Total investments at fair value	$	143,540	$	120,565

The following tables set forth by level, within the fair value hierarchy, the assetscarried at fair value as of December 31, 2012 and 2011.

	Assets at Fair Value as of December 31, 2012
(Dollars in thousands)	Level 1		Level 2		Level 3		Total
Pooled separate accounts	$	—	$	29,869	$	—	$	29,869
Mutual funds	98,269		—		—		98,269
Common stock	—		—		—		—
Guaranteed deposit account	—		—		15,402		15,402
Interest bearing cash	—		—		—		—
Total assets at fair value	$	98,269	$	29,869	$	15,402	$	143,540
	Assets at Fair Value as of December 31, 2011
(Dollars in thousands)	Level 1		Level 2		Level 3		Total
Pooled separate accounts	$	—	$	32,072	$	—	$	32,072
Mutual funds	47,255		—		—		47,255
Common stock	27,804		—		—		27,804
Guaranteed deposit account	—		—		13,266		13,266
Interest bearing cash	168		—		—		168
Total assets at fair value	$	75,227	$	32,072	$	13,266	$	120,565

Changes in fair value of Level 3 assets [Table Text Block]

The table below sets forth a summary of changes in the fair value of the guaranteed deposit account's Level 3 assetsfor the year ended December 31, 2012.

(Dollars in thousands)	Guaranteed Deposit Account
Balance at beginning of year	$	13,266
Realized gains (losses)	—
Unrealized gains relating to instruments still held at the reporting date	1,256
Purchases, sales, issuances and settlements (net)	880
Transfers in and/or out of Level 3	—
Balance at end of year	$	15,402

Schedule of future benefit payments [Table Text Block]

	Pension Benefits		Retiree Health and Life Insurance Benefits
2013	$	7,687	$	1,238
2014	7,467		1,229
2015	7,753		1,218
2016	8,060		1,183
2017	8,548		1,118
2018-2022	52,571		6,155