Loans and Allowance for Loan Losses - Industry Classification System (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Percentage of credit exposure to risk based capital	25.00%
Lessors of nonresidential buildings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Principal Balances	$ 2,778,454
Unfunded Commitments	32,497
Total exposure	2,810,951	$ 1,701,853
Lessors of residential buildings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Principal Balances	870,777
Unfunded Commitments	13,467
Total exposure	884,244	874,234
Hotels and motels
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Principal Balances	627,126
Unfunded Commitments	1,865
Total exposure	$ 628,991	$ 291,865