Significant Accounting Policies Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset			$ 165,500	$ 170,500
Operating Lease, Liability			$ 171,800	$ 174,400
Cumulative Effect of New Accounting Principle in Period of Adoption					$ (12,611)	$ (2,285)
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption					$ (12,611)	$ (2,285)
Two Thousand And Nineteen [Member] | Scenario, Forecast [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Additional premium amortization expense on securities	$ 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
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