Securities - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sale of debt securities available for sale			$ 31,694	$ 235,613	$ 40,421
Gross gains from sale of securities			200	1,600	500
Gross losses from sale of securities			700	1,500	100
Unrealized losses from securities transferred from available for sale to held to maturity						$ 3,100
Unamortized balance of securities transferred from available for sale to held to maturity			700
Fair value for securities in unrealized loss position for less than twelve months	$ 326,177		478,423	326,177
Unrealized losses on securities in unrealized loss position for less than twelve months	2,134		7,140	2,134
Fair value for securities in unrealized loss position for twelve months or more	440,333		646,354	440,333
Unrealized losses on securities in unrealized loss position for more than twelve months	10,540		19,538	10,540
Unrealized losses on mortgage backed securities of government sponsored entities	12,674		26,678	12,674
Fair value of mortgage backed securities of government sponsored entities	$ 766,510		1,124,777	$ 766,510
Other assets of Federal Home Loan Bank and Federal Reserve Bank			44,500
Other assets			$ 6,200
Shares held (in shares)	46,917,735		51,361,079	46,917,735
Number of shares acquired (in shares)		200,000
Payments to acquire Visa class b stock		$ 6,200	$ 0	$ 6,180	0
Gain on sale of securities	$ 15,200		$ 0	15,153	$ 0
Common Class B | Visa
Schedule of Available-for-sale Securities [Line Items]
Shares held (in shares)			11,330
Common Class A | Visa
Schedule of Available-for-sale Securities [Line Items]
Conversion rate of Class A stock for each share of Class B stock (in shares)			$ 1.6298
Shares of class A Visa stock issued (in shares)			18,465
Available-for-sale Securities
Schedule of Available-for-sale Securities [Line Items]
Fair value for securities in unrealized loss position for less than twelve months	22,900		$ 35,700	22,900
Unrealized losses on securities in unrealized loss position for less than twelve months	200		100	200
Fair value for securities in unrealized loss position for twelve months or more	15,300		31,300	15,300
Unrealized losses on securities in unrealized loss position for more than twelve months	400		1,100	400
CRA - Qualified Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Gross losses from sale of securities			100
Mortgage-backed securities and collateralized mortgage obligations of US Government Sponsored Entities
Schedule of Available-for-sale Securities [Line Items]
Fair value for securities in unrealized loss position for less than twelve months	304,723		200,184	304,723
Unrealized losses on securities in unrealized loss position for less than twelve months	2,047		2,235	2,047
Fair value for securities in unrealized loss position for twelve months or more	413,725		623,420	413,725
Unrealized losses on securities in unrealized loss position for more than twelve months	10,146		19,136	10,146
Unrealized losses on mortgage backed securities of government sponsored entities	12,193		21,371	12,193
Fair value of mortgage backed securities of government sponsored entities	718,448		823,604	718,448
Private collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Fair value for securities in unrealized loss position for less than twelve months	0		20,071	0
Unrealized losses on securities in unrealized loss position for less than twelve months	0		344	0
Fair value for securities in unrealized loss position for twelve months or more	20,744		12,739	20,744
Unrealized losses on securities in unrealized loss position for more than twelve months	338		187	338
Unrealized losses on mortgage backed securities of government sponsored entities	338		531	338
Fair value of mortgage backed securities of government sponsored entities	20,744		32,810	20,744
Collateralized loan obligations
Schedule of Available-for-sale Securities [Line Items]
Fair value for securities in unrealized loss position for less than twelve months	14,933		238,894	14,933
Unrealized losses on securities in unrealized loss position for less than twelve months	68		4,319	68
Fair value for securities in unrealized loss position for twelve months or more	0		0	0
Unrealized losses on securities in unrealized loss position for more than twelve months	0		0	0
Unrealized losses on mortgage backed securities of government sponsored entities	68		4,319	68
Fair value of mortgage backed securities of government sponsored entities	$ 14,933		238,894	$ 14,933
Carrying Value | United States Treasury Deposits and Other Public and Trust Deposits
Schedule of Available-for-sale Securities [Line Items]
Fair value of securities pledged as collateral			180,900
Carrying Value | Repurchase Agreement
Schedule of Available-for-sale Securities [Line Items]
Fair value of securities pledged as collateral			$ 214,300