Shareholders' Equity Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Beginning Balance	$ (59,063)	$ (32,974)	$ (38,449)
Other comprehensive income before reclassifications	55,302	(22,704)	10,008
Amounts reclassified from accumulated other comprehensive income (loss)	(2,661)	1,618	(4,533)
Amortization of net unrealized losses on AFS transferred to HTM	6,285	2,098
Reclassification of stranded tax effects		(7,101)
Ending Balance	(137)	(59,063)	(32,974)
Unrealized Gain (Losses) on Investment Securities Not Other-Than-Temporarily Impaired
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Beginning Balance	(44,654)	(18,509)	(23,047)
Other comprehensive income before reclassifications	56,919	(24,326)	10,432
Amounts reclassified from accumulated other comprehensive income (loss)	(3,686)	(30)	(5,894)
Amortization of net unrealized losses on AFS transferred to HTM	6,285	2,098
Reclassification of stranded tax effects		(3,887)
Ending Balance	14,864	(44,654)	(18,509)
Unrealized Non-Credit Gains (Losses) on Other-Than-Temporarily Impaired Debt Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Beginning Balance	680	458	273
Other comprehensive income before reclassifications	(680)	222	185
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Amortization of net unrealized losses on AFS transferred to HTM	0	0
Reclassification of stranded tax effects		0
Ending Balance	0	680	458
Total
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Beginning Balance	(15,089)	(14,923)	(15,675)
Other comprehensive income before reclassifications	(937)	1,400	(609)
Amounts reclassified from accumulated other comprehensive income (loss)	1,025	1,648	1,361
Amortization of net unrealized losses on AFS transferred to HTM	0	0
Reclassification of stranded tax effects		(3,214)
Ending Balance	$ (15,001)	$ (15,089)	$ (14,923)