New Accounting Standards Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 01, 2018	Jan. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in operating loss carryforward deferred tax assets		$ 24,035	$ 60,749
Decrease in accumulated other comprehensive income		(11,058)	7,116
Increase in other operations		242,628	242,014	$ 242,950
Increase in other interest		2,388	1,303	1,313
Increase in miscellaneous non-operating Income		715	1,292	2,062
Increase in miscellaneous non-operating deductions		$ 3,125	$ 3,699	$ 4,328
Federal statutory tax rate		35.00%	35.00%	35.00%
Potential Impact of Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in retained earnings						$ 200
Increase in operating loss carryforward deferred tax assets						$ 200
Potential Impact of Adopting Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in other operations		$ 8,200
Increase in other interest		15,800
Increase in miscellaneous non-operating Income		32,400
Increase in miscellaneous non-operating deductions		8,400
Potential Impact of Adopting Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in retained earnings		7,200
Decrease in accumulated other comprehensive income		$ 7,200
Subsequent Event | Potential Impact of Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in retained earnings					$ 41,000
Decrease in accumulated other comprehensive income					$ 41,000
Scenario, Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Federal statutory tax rate	21.00%