Retirement Plans (Changes in Accumulated Other Comprehensive Income (Loss) Related to Retirement Plans) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss) at beginning of year	$ (28,665)	$ (17,428)
Prior service credits	(196)
Net actuarial gain (loss)	(6,532)
Change in adjustment for pension and other postretirement benefits, net of tax benefit of $3,623, $6,051 and $928 for the years ended December 31, 2012, 2011 and 2010, respectively	(6,728)	(11,237)	(1,723)
Accumulated other comprehensive income (loss) at end of year	(35,393)	(28,665)	(17,428)
Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss) at beginning of year	(28,869)
Prior service credits	(1)
Net actuarial gain (loss)	(6,418)
Change in adjustment for pension and other postretirement benefits, net of tax benefit of $3,623, $6,051 and $928 for the years ended December 31, 2012, 2011 and 2010, respectively	(6,419)
Accumulated other comprehensive income (loss) at end of year	(35,288)
Postretirement Plan [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss) at beginning of year	513
Prior service credits	(195)
Net actuarial gain (loss)	(35)
Change in adjustment for pension and other postretirement benefits, net of tax benefit of $3,623, $6,051 and $928 for the years ended December 31, 2012, 2011 and 2010, respectively	(230)
Accumulated other comprehensive income (loss) at end of year	283
Supplemental Plan [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss) at beginning of year	(309)
Prior service credits	0
Net actuarial gain (loss)	(79)
Change in adjustment for pension and other postretirement benefits, net of tax benefit of $3,623, $6,051 and $928 for the years ended December 31, 2012, 2011 and 2010, respectively	(79)
Accumulated other comprehensive income (loss) at end of year	$ (388)