Investments in Qualified Affordable Housing Partnerships, Tax Credit and Other Investments, Net (Investments in Tax Credit and Other Investments, Net) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Investments in Tax Credit and Other Investments, Net [Line Items]
Investments in tax credit and other investments, net	$ 232,194		$ 232,194		$ 224,551
Amortization expense included in noninterest expense	20,789	$ 23,827	58,670	$ 66,059
Marketable equity securities					31,900
Unrealized loss recognized on marketable equity securities held	(185)		(798)
Investments in tax credit and other investments, net
Investments in Tax Credit and Other Investments, Net [Line Items]
Marketable equity securities	30,800		30,800
Accrued expenses and other liabilities
Investments in Tax Credit and Other Investments, Net [Line Items]
Accrued expenses and other liabilities — Unfunded commitments	$ 94,222		$ 94,222		$ 113,372