Held-to-Maturity Securities Proceeds from Sale and Gross Gains and Losses on HTM Securities (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Held-to-maturity, Sale, Excluding Other-than-temporary Impairment [Abstract]
Proceeds from sale of held-to-maturity securities	[1]	$ 185,177	$ 0	$ 0
Amortized cost of held-to-maturity securities	[1]	173,146	0	0
Realized net gain from sale of held-to-maturity securities	[1]	$ 12,031	$ 0	$ 0

[1] The securities sold had less than 15 percent of the acquired principal outstanding at the time of the sale. Such sales are treated as maturities for the purposes of security classification. The sale does not impact our ability and intent to hold the remaining investments classified as held-to-maturity through their stated maturity dates.