Securities - Securities Portfolio (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		$ 2,311,920
Amortized Cost			$ 1,907,826
Gross Unrealized Gains		4,405
Gross Unrealized Gains			1,406
Gross Unrealized Losses		(44,316)
Gross Unrealized Losses			(25,023)
Fair Value		2,272,009
Fair Value			1,884,209
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost		10,176	13,760
Fair Value		9,871	12,013
Debt and Equity Securities, FV-NI [Line Items]
Equity Securities		30,806	0
Trading Securities		0	20,447	[1]
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		37,925
Amortized Cost			46,529
Gross Unrealized Gains		17
Gross Unrealized Gains			0
Gross Unrealized Losses		(175)
Gross Unrealized Losses			(184)
Fair Value		37,767
Fair Value			46,345
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		144,125
Amortized Cost			157,636
Gross Unrealized Gains		45
Gross Unrealized Gains			197
Gross Unrealized Losses		(1,607)
Gross Unrealized Losses			(986)
Fair Value		142,563
Fair Value			156,847
Collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		1,336,531
Amortized Cost			1,113,019
Gross Unrealized Gains		3,362
Gross Unrealized Gains			121
Gross Unrealized Losses		(24,684)
Gross Unrealized Losses			(17,954)
Fair Value		1,315,209
Fair Value			1,095,186
Other Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		477,665
Amortized Cost			373,676
Gross Unrealized Gains		520
Gross Unrealized Gains			201
Gross Unrealized Losses		(11,251)
Gross Unrealized Losses			(4,334)
Fair Value		466,934
Fair Value			369,543
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		229,600
Amortized Cost			209,558
Gross Unrealized Gains		461
Gross Unrealized Gains			693
Gross Unrealized Losses		(2,874)
Gross Unrealized Losses			(1,260)
Fair Value		227,187
Fair Value			208,991
Schedule of Held-to-Maturity Securities [Line Items]
Amortized Cost		10,176	13,760
Gross Unrealized Gains		0	0
Gross Unrealized Losses		(305)	(1,747)
Fair Value		9,871	12,013
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		86,074
Amortized Cost			0
Gross Unrealized Gains		0
Gross Unrealized Gains			0
Gross Unrealized Losses		(3,725)
Gross Unrealized Losses			0
Fair Value		82,349
Fair Value			0
Equity securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]		7,408
Gross Unrealized Gains	[1]		194
Gross Unrealized Losses	[1]		(305)
Fair Value	[1]		$ 7,297
Debt and Equity Securities, FV-NI [Line Items]
Equity Securities	[1]	$ 30,806

[1] As a result of accounting guidance adopted in 2018, equity securities are no longer presented within trading securities or securities available-for-sale and are now presented within equity securities in the Consolidated Statements of Financial Condition for the current period. For further discussion of this guidance, see Note 2. "Recent Accounting Pronouncements."