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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Investments in Tax Credit and Other Investments, Net [Line Items]
Investments in tax credit and other investments, net	$ 242,595		$ 242,595		$ 224,551
Amortization expense included in noninterest expense	20,481	$ 27,872	37,881	$ 42,232
Marketable equity securities					31,900
Unrealized loss recognized on marketable equity securities held	(159)		(613)
Investments in tax credit and other investments, net
Investments in Tax Credit and Other Investments, Net [Line Items]
Marketable equity securities	30,900		30,900
Accrued expenses and other liabilities
Investments in Tax Credit and Other Investments, Net [Line Items]
Accrued expenses and other liabilities — Unfunded commitments	$ 109,432		$ 109,432		$ 113,372