Loans and Allowance for Loan Losses - Industry Classification System (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Lessors of nonresidential buildings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Principal Balances	$ 2,879,195
Unfunded Commitments	691,591
Total exposure	3,570,786	$ 2,810,951
Lessors of residential buildings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Principal Balances	929,097
Unfunded Commitments	275,564
Total exposure	1,204,661	884,244
Hotels (except for Casino Hotels) and Motels
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Principal Balances	678,619
Unfunded Commitments	195,623
Total exposure	$ 874,242	$ 628,991