Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Item Effected [Line Items]
Retained earnings	$ (370,521)	$ (339,959)
Assets	6,320,058	5,887,284
Liabilities and shareholders' equity	6,320,058	$ 5,887,284
Accounting Standards Update 2017-08
Item Effected [Line Items]
Retained earnings	300
Minimum | Accounting Standards Update 2016-02
Item Effected [Line Items]
Assets	10,000
Liabilities and shareholders' equity	10,000
Maximum | Accounting Standards Update 2016-02
Item Effected [Line Items]
Assets	20,000
Liabilities and shareholders' equity	20,000
Accounting Standards Update 2018-02
Item Effected [Line Items]
Reclassification of tax effects related to the Tax Cuts and Jobs Act	$ 720