Investment Securities - Available-For-Sale Investment (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Total debt securities available-for-sale
Amortized Cost	$ 3,347,679
Unrealized Gains	35,738
Unrealized Losses	13,545
Fair Value	3,369,872
Total
Amortized Cost	3,347,679	$ 3,069,645
Unrealized Gains		5,601
Unrealized Losses		53,414
Total	3,369,872	3,021,832
Government and government-sponsored enterprises
Total debt securities available-for-sale
Amortized Cost	297,284	354,342
Unrealized Gains	378	713
Unrealized Losses	1,936	3,355
Fair Value	295,726	351,700
State and political subdivisions
Total debt securities available-for-sale
Amortized Cost	428,365	523,178
Unrealized Gains	15,845	1,141
Unrealized Losses	125	8,033
Fair Value	444,085	516,286
Residential mortgage-backed securities
Total debt securities available-for-sale
Amortized Cost	351,790	216,990
Unrealized Gains	2,807	261
Unrealized Losses	975	3,823
Fair Value	353,622	213,428
Collateralized mortgage obligations
Total debt securities available-for-sale
Amortized Cost	1,930,699	1,623,415
Unrealized Gains	14,869	2,903
Unrealized Losses	5,873	25,020
Fair Value	1,939,695	1,601,298
Corporate bonds
Total debt securities available-for-sale
Amortized Cost	291,869	304,243
Unrealized Gains	1,337	259
Unrealized Losses	3,894	11,439
Fair Value	289,312	293,063
Trust preferred securities
Total debt securities available-for-sale
Amortized Cost	47,672	47,477
Unrealized Gains	502	324
Unrealized Losses	742	1,744
Fair Value	$ 47,432	$ 46,057

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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