Accounting Standards Updates Accounting Standards Update (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ (2,285)
Two Thousand And Nineteen [Member] | Scenario, Forecast [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset			$ 170,400
Operating Lease, Liability			174,400
Cumulative Effect of New Accounting Principle in Period of Adoption			$ 12,600
Investment Income, Amortization of Premium	$ 5,200
Minimum [Member] | Two Thousand And Nineteen [Member] | Scenario, Forecast [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset		$ 110,000
Operating Lease, Liability		110,000
Maximum [Member] | Two Thousand And Nineteen [Member] | Scenario, Forecast [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset		140,000
Operating Lease, Liability		$ 140,000