Disclosure About Fair Values of Financial Instruments - Summary of Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial Assets:
Interest-bearing deposits with banks	$ 322,786	$ 523,436
Federal funds sold	5,585	18,502
Investment securities available-for-sale	1,754,839	1,187,252
Derivative assets	182,287	11,136
Other assets	440,376	170,494
Financial Liabilities:
Advances from FHLB	395,000	150,000
Securities sold under agreements to repurchase	1,418	1,106
Senior debt	184,822	184,801
Subordinated debt	98,963	98,910
Junior subordinated debentures	37,075	36,953
Derivative liabilities	24,046	32,350
Level 1
Financial Assets:
Cash and due from banks	214,698	237,342
Interest-bearing deposits with banks	322,786	523,436
Federal funds sold	5,585	18,502
Equity securities with readily determinable fair values not held for trading	6,073	5,840
Level 2
Financial Assets:
Investment securities available-for-sale	1,754,839	1,187,252
Loans held for sale	209,346	59,461
Derivative assets	182,287	11,136
Financial Liabilities:
Deposits	14,210,340	10,700,350
Advances from FHLB	395,000	150,000
Securities sold under agreements to repurchase	1,418	1,106
Senior debt	186,967	194,762
Subordinated debt	105,479	103,008
Junior subordinated debentures	48,671	46,946
Derivative liabilities	24,046	32,350
Level 3
Financial Assets:
Net loans	13,119,074	9,735,130
Net profits interests	5,317	5,779
Other assets	59,987
Financial Liabilities:
Investments in limited partnerships		36,917
Fair Value
Financial Assets:
Cash and due from banks	214,698	237,342
Interest-bearing deposits with banks	322,786	523,436
Federal funds sold	5,585	18,502
Investment securities available-for-sale	1,754,839	1,187,252
Equity securities with readily determinable fair values not held for trading	6,073	5,840
Loans held for sale	209,346	59,461
Net loans	13,119,074	9,735,130
Derivative assets	182,287	11,136
Net profits interests	5,317	5,779
Other assets	59,987
Financial Liabilities:
Deposits	14,210,340	10,700,350
Advances from FHLB	395,000	150,000
Securities sold under agreements to repurchase	1,418	1,106
Senior debt	186,967	194,762
Subordinated debt	105,479	103,008
Junior subordinated debentures	48,671	46,946
Derivative liabilities	24,046	32,350
Investments in limited partnerships		36,917
Carrying Value
Financial Assets:
Cash and due from banks	214,698	237,342
Interest-bearing deposits with banks	322,786	523,436
Federal funds sold	5,585	18,502
Investment securities available-for-sale	1,754,839	1,187,252
Equity securities with readily determinable fair values not held for trading	6,073	5,840
Loans held for sale	209,346	59,461
Net loans	13,519,916	9,959,545
Derivative assets	182,287	11,136
Net profits interests	5,317	5,779
Other assets	59,987
Financial Liabilities:
Deposits	14,199,223	10,708,689
Advances from FHLB	395,000	150,000
Securities sold under agreements to repurchase	1,418	1,106
Senior debt	184,822	184,801
Subordinated debt	98,963	98,910
Junior subordinated debentures	37,075	36,953
Derivative liabilities	$ 24,046	32,350
Investments in limited partnerships		$ 36,917