Securities Financing Activities (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Securities purchased under agreements to resell
Securities purchased under agreements to resell, subject to master netting arrangement, gross amounts recognized		$ 227,584	$ 93,664
Securities purchased under agreements to resell, subject to a master netting arrangement, gross amounts offset in the condensed consolidated balance sheets		227,584	67,751
Securities purchased under agreements to resell, subject to a master netting arrangement, net amount presented in the condensed consolidated balance sheets		0	25,913
Securities purchased under agreements to resell, subject to a master netting arrangement, financial instruments collateral received/ pledged	[1]	0	25,913
Securities purchased under agreements to resell, net amount		0	0
Securities sold under agreements to repurchase
Securities sold under agreements to repurchase, subject to a master netting arrangement, gross amounts recognized		233,517	85,632
Securities sold under agreements to repurchase, gross amounts offset in the condensed consolidated balance sheets		227,584	67,751
Securities sold under agreements to repurchase, subject to a master netting arrangement, net amount presented in the condensed consolidated balance sheet		5,933	17,881
Securities sold under agreements to repurchase, subject to a master netting arrangement, financial instruments collateral received/ pledged	[1]	5,933	17,881
Securities sold under agreements to repurchase, subject to a master netting arrangement, net amount		0	0
Fair value of collateral received related to securities purchased under agreements to resell		228,000	94,000
Fair value of collateral pledged related to securities sold under agreements to repurchase		$ 238,000	$ 91,000

[1] The actual amount of collateral received/pledged is limited to the asset/liability balance and does not include excess collateral received/pledged. When excess collateral exists, the collateral shown in the table above has been allocated based on the percentage of the actual amount of collateral posted.