Consolidated Statement of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2010	$ 691,625	$ 342,978	$ 355,251	$ (6,604)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	61,848	0	63,044	(1,196)
Dividends paid on common stock	(46,690)	0	(46,690)	0
Tax expense from employee stock option plan	(26)	(26)	0	0
Stock-based compensation	1,769	1,769	0	0
Issuance of common stock	3,632	3,632	0	0
Common stock expense	0	30	(30)	0
Balance at Dec. 31, 2011	712,158	348,383	371,575	(7,800)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	57,288	0	58,779	(1,491)
Dividends paid on common stock	(48,007)	0	(48,007)	0
Tax expense from employee stock option plan	(149)	(149)	0	0
Stock-based compensation	1,291	1,291	0	0
Issuance of common stock	7,046	7,046	0	0
Balance at Dec. 31, 2012	729,627	356,571	382,347	(9,291)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	63,471	0	60,538	2,933
Dividends paid on common stock	(49,204)	0	(49,204)	0
Tax expense from employee stock option plan	(242)	(242)	0	0
Stock-based compensation	2,169	2,169	0	0
Issuance of common stock	6,051	6,051	0	0
Balance at Dec. 31, 2013	$ 751,872	$ 364,549	$ 393,681	$ (6,358)