Investment Securities - Narrative (Details)	3 Months Ended
	Mar. 31, 2017 USD ($) security	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Investments, Debt and Equity Securities [Abstract]
Net realized and unrealized gain (loss) on trading securities	$ 2,000,000	$ 40,000,000
Available for sale securities in unrealized loss, positions number of positions, less than twelve months | security	55
Available for sale securities in unrealized loss, positions number of positions, greater than twelve months | security	8
Proceeds from sales of available for sale securities	$ 2,652,000	19,839,000
Impairment charges	0	$ 0
Investment securities, carrying value	$ 91,100,000		$ 95,199,000