Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for credit losses on HTM	$ 2,915	$ 0
Available-for-sale, allowance for credit loss	312	0
Available-for-sale, amortized cost	$ 3,397,043	$ 3,263,151
Preferred stock, Series D, shares authorized (in shares)	40,040,000	40,040,000
Preferred stock, Series D, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, Series D, liquidation value (in dollars per share)	$ 1,000	$ 1,000
Preferred stock, Series D, shares issued (in shares)	767	767
Preferred stock, Series D, shares outstanding (in shares)	767	767
Common stock, Class A, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, Class A, shares authorized (in shares)	175,000,000	175,000,000
Common stock, Class A, shares issued (in shares)	108,077,662	113,628,601
Common stock, Class A, shares outstanding (in shares)	108,077,662	113,628,601