Condensed Consolidated Statements of Changes in Owners' Equity Statement - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]
Beginning balance at Dec. 31, 2016	$ 1,445,965	$ 659	$ 1,561,695	$ (6,558)	$ (35,917)	$ (73,914)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	483	0	(1,650)	0	2,133	0
Net income (loss)	(19,769)				(19,769)
Other Comprehensive Income (Loss), Net of Tax	24,215		0			24,215
Dividends	(94,714)		(94,714)
Dividends, Share-based Compensation, Cash	(818)		(818)		0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	8,377		8,377		0
Stock Issued During Period, Value, Acquisitions	330,341	124	330,217		0
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures	1,172	2	1,170			0
Treasury Stock, Value, Acquired, Cost Method	(1,361)			(1,361)
Ending balance at Sep. 30, 2017	1,693,891	785	1,804,277	(7,919)	(53,553)	(49,699)
Beginning balance at Jun. 30, 2017	1,405,399	661	1,505,941	(7,824)	(34,450)	(58,929)
Net income (loss)	(19,103)				(19,103)
Other Comprehensive Income (Loss), Net of Tax	9,230	0				9,230
Dividends	(35,221)		(35,221)
Dividends, Share-based Compensation, Cash	(221)		(221)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	2,907		2,907		0
Stock Issued During Period, Value, Acquisitions	330,341	124	330,217		0
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures	654		654
Treasury Stock, Value, Acquired, Cost Method	(95)			(95)
Ending balance at Sep. 30, 2017	1,693,891	785	1,804,277	(7,919)	(53,553)	(49,699)
Beginning balance at Dec. 31, 2017	1,658,365	786	1,770,117	(8,031)	(50,706)	(53,801)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	11,513	0	0	0	11,513	0
Net income (loss)	(27,300)				(27,300)
Other Comprehensive Income (Loss), Net of Tax	27,703					27,703
Dividends	(122,468)		(122,468)
Dividends, Share-based Compensation, Cash	(406)		(406)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	8,246		8,246
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures	1,031	2	1,029
Treasury Stock, Retired, Cost Method, Amount	0	(2)	0	8,031	(8,029)	0
Treasury Stock, Value, Acquired, Cost Method	(699)			(699)
Ending balance at Sep. 30, 2018	1,555,985	786	1,656,518	(699)	(74,522)	(26,098)
Beginning balance at Jun. 30, 2018	1,584,518	785	1,696,865	(699)	(82,983)	(29,450)
Net income (loss)	8,461				8,461
Other Comprehensive Income (Loss), Net of Tax	3,352					3,352
Dividends	(43,215)		(43,215)
Dividends, Share-based Compensation, Cash	(342)		(342)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	2,701		2,701
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures	510	1	509
Ending balance at Sep. 30, 2018	$ 1,555,985	$ 786	$ 1,656,518	$ (699)	$ (74,522)	$ (26,098)