Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period	$ 382,762	$ 382,537	$ 382,762	$ 382,537
Goodwill, Purchase Accounting Adjustments	0	225	0	225
Total goodwill, end of period	382,762	382,762	382,762	382,762
CDI current period amortization	(1,460)	(1,695)	(4,526)	(5,230)
Indefinite-Lived Intangible Assets (Excluding Goodwill)	919	919	919	919
Other intangible assets, net	19,051	25,229	19,051	25,229		$ 23,577
Total goodwill and intangible assets, end of period	401,813	407,991	$ 401,813	407,991
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					$ (39,006)	$ (35,940)	$ (32,593)	$ (29,058)
Core deposit intangible, net, beginning of period	19,592	26,005	$ 22,658	29,540
CDI current period amortization	(1,460)	(1,695)	(4,526)	(5,230)
Total core deposit intangible, end of period	$ 18,132	$ 24,310	$ 18,132	$ 24,310