Recently Issued Accounting Pronouncements (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease to retained earnings	$ 361,242	$ 396,051	$ 396,051
Allowance for credit losses on loans	115,422		35,698	$ 37,856	$ 36,072
Deferred income taxes, net	15,249		0
Loans held for investment	8,754,869		8,722,311
Allowance for credit losses on off-balance sheet credit exposures		3,279
Operating lease liabilities	56,252		46,498
Operating lease right of use assets	52,572		43,177
Commercial loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans		20,118
Loans held for investment	$ 2,023,027		$ 1,975,053
Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease to retained earnings		(45,600)
Allowance for credit losses on loans		64,000
Deferred income taxes, net		18,300
Loans held for investment		55,700
Allowance for credit losses on off-balance sheet credit exposures		8,300
Accounting Standards Update 2016-13 | Commercial loans | Investor loans secured by real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans		16,100
Accounting Standards Update 2016-13 | Commercial loans | Business loans secured by real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans		27,600
Accounting Standards Update 2016-13 | Commercial loans | Commercial loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans		9,500
Accounting Standards Update 2016-13 | Consumer loans | Retail loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans		$ 2,500