Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt securities available for sale and interest-only strips
Net unrealized gains (losses) arising during the period, before tax	$ 164,863	$ 109,403	$ (16,373)
Net unrealized gains (losses) arising during the period, tax effect	(39,674)	(25,707)	4,002
Net unrealized gains (losses) arising during the period, net of tax	125,189	83,696	(12,371)
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), before tax	1,547	642	1,029
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), tax effect	(346)	(218)	(327)
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), net of tax	1,201	424	702
Net unrealized gains (losses) on debt securities available for sale and interest-only strips, before taxes	166,410	110,045	(15,344)
Net unrealized gains (losses) on debt securities available for sale and interest-only strips, tax effect	(40,020)	(25,925)	3,675
Net unrealized gains (losses) on debt securities available for sale and interest-only strips, net of tax	126,390	84,120	(11,669)
Recognized postretirement prior service costs
Net unrealized gains (losses) arising during the period, before tax	449
Net unrealized gains (losses) arising during the period, tax effect	(107)
Net unrealized gains (losses) arising during the period, net of tax	342
Reclassification of amortization of prior service cost to Other non-interest expense, before tax	(46)	(46)	(46)
Reclassification of amortization of prior service cost to Other non-interest expense, tax effect	11	13	12
Reclassification of amortization of prior service cost to Other non-interest expense, net of tax	(35)	(33)	(34)
Net unrealized gains (losses) on recognized postretirement prior service cost, net of tax	307
Net unrealized gains (losses) on recognized postretirement prior service cost, before tax	403
Net unrealized gains (losses) on recognized postretirement prior service cost, tax effect	(96)
Net investment hedges
Net unrealized gains (losses) on net investment hedges, before tax	(5,452)	(7,001)	13,762
Net unrealized gains (losses) on net investment hedges, before tax	1,257	1,815	(3,312)
Net unrealized gains (losses) on net investment hedges, net of tax	(4,195)	(5,186)	10,450
Foreign currency translation adjustment
Foreign currency translation adjustment, before tax	5,894	8,514	(13,368)
Foreign currency translation adjustment, tax effect	0	0	0
Foreign currency translation adjustment, net of tax	5,894	8,514	(13,368)
Total other comprehensive income (loss), before tax	167,255	111,512	(14,996)
Total other comprehensive income (loss), tax effect	(38,859)	(24,097)	375
Total other comprehensive income (loss), net of tax	128,396	87,415	(14,621)
Total interest income
Debt securities available for sale and interest-only strips
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), before tax	3,827	2,644	1,066
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), tax effect	(885)	(716)	(335)
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), net of tax	2,942	1,928	731
Gains (losses) on debt securities, net
Debt securities available for sale and interest-only strips
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), before tax	(2,309)	(1,517)	(127)
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), tax effect	549	369	31
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), net of tax	(1,760)	(1,148)	(96)
Other noninterest expense
Debt securities available for sale and interest-only strips
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), before tax	29	(485)	90
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), tax effect	(10)	129	(23)
Reclassification of net (gains) losses from accumulated other comprehensive income (loss), net of tax	$ 19	$ (356)	$ 67