Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period			$ 382,762
Total goodwill, end of period	$ 382,762	$ 382,762	382,762	$ 382,762
CDI current period amortization	(1,188)	(1,460)	(3,786)	(4,526)
Indefinite-Lived Intangible Assets (Excluding Goodwill)	919	919	919	919
Other intangible assets, net	13,845	19,051	13,845	19,051		$ 17,631
Total goodwill and intangible assets, end of period	396,607	401,813	$ 396,607	401,813
Core Deposits [Member]
Goodwill and Intangible Assets [Line Items]
Estimated life of CDI, in years			10 years
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period					$ 58,598	58,598	$ 58,598	$ 58,598
Accumulated amortization at beginning of period					$ (44,484)	$ (41,886)	$ (39,006)	$ (35,940)
Core deposit intangible, net, beginning of period	14,114	19,592	$ 16,712	22,658
CDI current period amortization	(1,188)	(1,460)	(3,786)	(4,526)
Total core deposit intangible, end of period	$ 12,926	$ 18,132	$ 12,926	$ 18,132