Credit Arrangements and Debt Obligations Derivative Assets at Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	$ (960)	$ 1,525	$ (9,409)	$ 10,788
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	443	240	1,923	(95)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax	(1,403)	1,285	(11,332)	10,883
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	(258)	415	(2,531)	2,934
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	119	65	517	(26)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	377	(350)	3,048	(2,960)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(702)	1,110	(6,878)	7,854
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	324	175	1,406	(69)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	(1,026)	$ 935	(8,284)	$ 7,923
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	$ (3,400)		$ (3,400)
Derivative Asset					$ 7,900