Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Item Effected [Line Items]
Assets	$ 5,806,735	$ 5,486,268
Liabilities and shareholders' equity	$ 5,806,735	5,486,268
Minimum | Accounting Standards Update 2016-02
Item Effected [Line Items]
Assets		12,000
Liabilities and shareholders' equity		12,000
Maximum | Accounting Standards Update 2016-02
Item Effected [Line Items]
Assets		15,000
Liabilities and shareholders' equity		$ 15,000