Recent Accounting Standards (Narrative) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Cumulative effect adjustment	$ 1,704,496	$ 1,672,020	$ 1,683,026	$ 1,538,049	$ 1,483,799	$ 1,441,339
Decrease to deferred income tax liability	96,502		37,814
Decrease to retained earnings	$ 3,004,960		2,921,448
Accounting Standards Update 2016-13 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Cumulative effect adjustment			(1,051)
Increase to allowance for credit losses			1,414
Decrease to deferred income tax liability			(363)
Decrease to retained earnings			$ (1,051)