Other Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Other Assets [Abstract]
Cash Surrender Value of Life Insurance	$ 195,911		$ 193,917
Interest and fees receivable income	81,816		82,935
Income Taxes Receivable	37,022		98,998
Equity Method Investments, Other Asset Investments	54,474	$ 1,200	49,432
Low Income Housing Tax Credit - LIHTC	48,468		39,235
Equity Investments Without Readily Determinable Fair Value	15,525		14,856
Equity Investments With Readily Determinable Fair Value	4,569		0
Prepaid Expense	20,153		17,800
Other Assets, Miscellaneous	37,708		43,550
Other Assets	$ 495,646		$ 540,723