Consolidated Statement of Changes in Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Non-controlling Interest	Comprehensive Income
Balance at Dec. 31, 2008	$ 75,285	$ 295	$ 129,284		$ (59,479)	$ 5,185
Balance (in shares) at Dec. 31, 2008		29,488,408
Increase (Decrease) in Stockholders' Equity
Dividends on common stock	(45,926)		(21,021)	(24,905)
Shares issued under employee plan, net of forfeitures	1	1
Shares issued under employee plan, net of forfeitures (in shares)		154,752
Non-cash, stock-based compensation	1,927		1,927
Purchase and retirement of common stock	(545)		(545)
Purchase and retirement of common stock (in shares)		(34,507)
Tax on restricted stock vesting	198		198
Pension tax adjustment	(97)		(97)
Comprehensive income (loss):
Net income	25,935			24,905		1,030	25,935
Change in prior service cost and net loss, net of tax of $8,434, $948 and $8,345 for the years ended December 31, 2011, 2010 and 2009, respectively	14,022				14,022		14,022
Change in fair value of cash flow hedges, net of tax of $4,434, $1,430 and $5,707 for the years ended December 31, 2011, 2010 and 2009, respectively	9,917				9,917		9,917
Total comprehensive income	49,874						49,874
Balance at Dec. 31, 2009	80,717	296	109,746		(35,540)	6,215
Balance (in shares) at Dec. 31, 2009		29,608,653
Increase (Decrease) in Stockholders' Equity
Dividends on common stock	(46,179)		(13,584)	(32,595)
Shares issued under employee plan, net of forfeitures	2	2
Shares issued under employee plan, net of forfeitures (in shares)		208,007
Non-cash, stock-based compensation	2,363		2,363
Purchase and retirement of common stock	(1,001)		(1,001)
Purchase and retirement of common stock (in shares)		(53,538)
Tax on restricted stock vesting	602		602
Distributions to non-controlling interests	(1,850)					(1,850)
Comprehensive income (loss):
Net income	33,152			32,595		557	33,152
Change in prior service cost and net loss, net of tax of $8,434, $948 and $8,345 for the years ended December 31, 2011, 2010 and 2009, respectively	1,572				1,572		1,572
Change in fair value of cash flow hedges, net of tax of $4,434, $1,430 and $5,707 for the years ended December 31, 2011, 2010 and 2009, respectively	2,497				2,497		2,497
Total comprehensive income	37,221						37,221
Balance at Dec. 31, 2010	71,875	298	98,126		(31,471)	4,922
Balance (in shares) at Dec. 31, 2010		29,763,122
Increase (Decrease) in Stockholders' Equity
Dividends on common stock	(46,348)		(19,938)	(26,410)
Shares issued under employee plan, net of forfeitures	1	1
Shares issued under employee plan, net of forfeitures (in shares)		145,383
Non-cash, stock-based compensation	2,132		2,132
Purchase and retirement of common stock	(726)		(726)
Purchase and retirement of common stock (in shares)		(38,993)
Tax on restricted stock vesting	258		258
Comprehensive income (loss):
Net income	26,982			26,410		572	26,982
Change in prior service cost and net loss, net of tax of $8,434, $948 and $8,345 for the years ended December 31, 2011, 2010 and 2009, respectively	(13,959)				(13,959)		(13,959)
Change in fair value of cash flow hedges, net of tax of $4,434, $1,430 and $5,707 for the years ended December 31, 2011, 2010 and 2009, respectively	7,597				7,597		7,597
Total comprehensive income	20,620						20,620
Balance at Dec. 31, 2011	$ 47,812	$ 299	$ 79,852		$ (37,833)	$ 5,494
Balance (in shares) at Dec. 31, 2011		29,869,512