Retirement Plans and Other Postretirement Benefits (Tables)

12 Months Ended

Dec. 31, 2012

Retirement Plans and Other Postretirement Benefits [Abstract]

Summary of retirement plans and other postretirement benefits

	Retirement Plans						Other  Postretirement Benefits
(Dollars in thousands)	2012			2011			2012			2011
Change in benefit obligation:
Benefit obligation at beginning of year	$	38,374		$	32,250		$	2,344		$	1,974
Service cost		622			556			82			66
Interest cost		1,726			1,725			116			117
Actuarial loss		3,755			5,368			55			267
Benefits paid		(1,598	)		(1,525	)		(79	)		(80	)
Benefit obligation at end of year	$	42,879		$	38,374		$	2,518		$	2,344
Change in plan assets:
Fair value of plan assets at beginning of year	$	25,213		$	24,366		$	—		$	—
Actual return on plan assets		2,669			127			—			—
Benefits paid		(1,598	)		(1,525	)		(79	)		(80	)
Employer contribution and non-qualified benefit payments		8,136			2,245			79			80
Fair value of plan assets at end of year		34,420			25,213			—			—
Funded status		(8,459	)		(13,161	)		(2,518	)		(2,344	)
Unrecognized net actuarial loss		22,576			20,482			850			819
Unrecognized prior service costs		(1,825	)		(2,061	)		(27	)		(48	)
Net amount recognized	$	12,292		$	5,260		$	(1,695	)	$	(1,573	)

Information for the pension plans with an accumulated benefit obligation in excess of plan assets

	At December 31,
(Dollars in thousands)	2012		2011
Projected benefit obligation	$	41,459	$	37,307
Accumulated benefit obligation		39,912		35,286
Fair value of plan assets		34,420		25,213

Components of net periodic benefit cost

	Retirement Plans									Other Postretirement Benefits
(Dollars in thousands)	2012			2011			2010			2012			2011			2010
Service cost	$	622		$	556		$	362		$	82		$	66		$	76
Interest cost		1,726			1,725			1,708			116			117			115
Expected return on plan assets		(2,254	)		(1,895	)		(1,670	)		—			—			—
Amortization of net loss		1,147			728			686			23			15			7
Accretion of prior service cost		(235	)		(235	)		(236	)		(20	)		(20	)		(20	)
Net periodic benefit cost	$	1,006		$	879		$	850		$	201		$	178		$	178

Expected amortization expense for 2013

(Dollars in thousands)	Retirement Plans			Other Postretirement Benefits
Expected amortization expense for 2013:
Amortization (accretion) of net loss	$	1,247		$	(24	)
(Accretion) amortization of prior service cost		(241	)		20

Summary of benefit payments expected to be paid

(Dollars in thousands) For the fiscal year ending:	Retirement Plans		Other Postretirement Benefits
2013	$	1,905	$	82
2014		1,955		111
2015		2,142		122
2016		2,268		128
2017		2,310		135
Years 2018-2022		11,068		750

Weighted-average assumptions used to determine benefit obligations

	Retirement Plans						Other  Postretirement Benefits
	2012			2011			2012			2011
Assumed discount rate		4.0	%		4.5	%		4.0	%		4.5	%
Assumed salary increase rate		3.0			3.0			—			—

	Retirement Plans						Other  Postretirement Benefits
	2012			2011			2012			2011
Assumed discount rate		4.5	%		5.5	%		4.5	%		5.5	%
Assumed long-term rate of investment return		8.0			8.0			—			—
Assumed salary increase rate		3.0			3.0			—			—

Summary of assumed health care cost trend rates

Assumed Health Care Cost Trend Rates	2012			2011			2010
Health care cost trend rate assumed for next year		6.5	%		6.5	%		6.5	%
Rate to which the cost trend rate is assumed to decline		5.0			5.0			5.0
Year that the rate reaches the ultimate rate		2014			2013			2012

Effect of one percentage-point change in the assumed health care cost trend rates

	One Percentage Point
(Dollars in thousands)	Increase		Decrease
Effect on total of service and interest cost components	$	8	$	(7	)
Effect on postretirement benefit obligation		97		(86	)

Summary of corporation's pension plan asset allocation

	Percentage of Plan Assets at December 31,
	2012			2011
Asset Category:
Equity securities		59	%		49	%
Debt securities		38			47
Other		3			4
Total		100	%		100	%

Major categories of assets in Corporation's pension plan

(Dollars in thousands)	Fair Value  Measurements at December 31,
	2012		2011
Level 1:
Common stocks	$	—	$	8,056
Mutual funds:
U.S. Large Cap		12,880		—
U.S. Mid Cap		1,649		986
U.S. Small Cap		1,675		991
International		4,164		2,202
Income		899		1,577
Short-term investments		916		1,250
Level 2:
U.S. government obligations		2,834		2,359
Corporate bonds		4,900		4,203
Level 3:
Certificates of deposit		4,503		3,589
Total fair value of plan assets	$	34,420	$	25,213

Reconciliation of the beginning and ending balances for measurements in hierarchy Level 3

(Dollars in thousands)	Balance at December 31, 2011		Total Unrealized Gains or (Losses)		Total Realized Gains or (Losses)		Purchases		Maturities/ Redemptions			Balance at December 31, 2012
Certificates of deposit	$	3,589	$	—	$	—	$	1,509	$	(595	)	$	4,503
Total Level 3 assets	$	3,589	$	—	$	—	$	1,509	$	(595	)	$	4,503

(Dollars in thousands)	Balance at December 31, 2010		Total Unrealized Gains or (Losses)		Total Realized Gains or (Losses)		Purchases		Maturities/ Redemptions			Balance at December 31, 2011
Certificates of deposit	$	2,898	$	—	$	—	$	1,305	$	(614	)	$	3,589
Total Level 3 assets	$	2,898	$	—	$	—	$	1,305	$	(614	)	$	3,589