Consolidated Statement Of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Cumulative Dividends In Excess Of Net Income [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Parent [Member]	Noncontrolling Interest [Member]
Balance, value at Dec. 31, 2012	$ 468,047	$ 279	$ 467,843	$ (18,495)	$ 7,555	$ 457,182	$ 10,865
Balance, shares at Dec. 31, 2012		27,857,217
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to common stockholders	78,408			78,408	1,415	79,823	664
Comprehensive income	80,487
Distributions to noncontrolling interest	(818)						(818)
Shares issued on stock options exercised, shares		18,959
Shares issued on stock options exercised, value	146	0	146			146
Share-based Compensation			2,086
Share-based compensation	2,086					2,086
Assignment of net assets in equity-method investee	817		817			817
Dividends declared, $1.43 per share	(60,352)			(60,352)		(60,352)
Balance, value at Sep. 30, 2013	$ 490,413	$ 279	$ 470,892	$ (439)	$ 8,970	$ 479,702	$ 10,711
Balance, shares at Sep. 30, 2013	27,876,176	27,876,176