Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net Income	$ 121,131	$ 116,127	$ 112,755
Other Comprehensive (Loss) Income, Net of Tax
Unrealized (losses) gains on available-for-sale securities	(21,407)	(22,845)	31,569
Reclassification adjustment for losses included in net income	1,335	(69)	204
Net unrealized (losses) gains on available-for-sale securities	(20,072)	(22,914)	31,773
Tax effect	7,776	8,904	(12,313)
Net of tax amount	(12,296)	(14,010)	19,460
Unrealized losses on derivatives used for cash flow hedges	(1,643)	(7,857)	(19,557)
Reclassification adjustment for losses included in net income	6,417	5,025	993
Net unrealized gains (losses) on derivatives used for cash flow hedges	4,774	(2,832)	(18,564)
Tax effect	(1,849)	1,087	7,203
Net of tax amount	2,925	(1,745)	(11,361)
Total other comprehensive (loss) income, net of tax	(9,371)	(15,755)	8,099
Total Comprehensive Income	$ 111,760	$ 100,372	$ 120,854