Accumulated Other Comprehensive Loss, Net of Tax (Schedule of Reclassifications from AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Impairment loss on securities recognized in earnings	$ (28)	$ (82)	$ 0	$ 0	$ (899)	$ (85)	$ (73)	$ (88)	$ (110)	$ (1,145)	$ (7,277)
Net of tax	52,579	51,536	52,503	49,722	51,006	50,457	47,834	50,429	206,340	199,726	179,456
Total interest expense	$ (24,820)	$ (23,988)	$ (23,459)	$ (23,148)	$ (23,103)	$ (22,544)	$ (22,375)	$ (22,478)	(95,415)	(90,500)	(90,912)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax									(7,198)	(2,479)	(12,247)
Available For Sale and Transferred Securities [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax									316	2,773	(4,214)
Available For Sale and Transferred Securities [Member] | Reclassification out of accumualted comprehensive income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of investment securities, net									609	5,499	712
Income tax expense									(183)	(1,581)	2,351
Net of tax									316	2,773	(4,214)
Accumulated Other-than-Temporary Impairment Attributable to Parent [Member] | Reclassification out of accumualted comprehensive income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Impairment loss on securities recognized in earnings									(110)	(1,145)	(7,277)
Derivative Instruments [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax									(5,686)	(5,182)	(5,952)
Derivative Instruments [Member] | Reclassification out of accumualted comprehensive income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense									3,279	2,918	3,320
Net of tax									(5,686)	(5,182)	(5,952)
Total interest expense									(8,965)	(8,100)	(9,272)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Compensation and benefits									(2,809)	(37)	(3,169)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Compensation and benefits									(73)	(73)	(73)
Defined benefit pension and postretirement benefit plans [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense									1,054	40	1,161
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax									$ (1,828)	$ (70)	$ (2,081)