Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period	$ 382,762
Total goodwill, end of period	382,762	$ 382,537
CDI current period amortization	(1,583)	(1,817)
Indefinite-Lived Intangible Assets (Excluding Goodwill)	919	919
Other intangible assets, net	21,994	28,642	$ 23,577
Total goodwill and intangible assets, end of period	$ 404,756	411,179
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
Accumulated amortization at beginning of period			$ (35,940)	$ (29,058)
Core deposit intangible, net, beginning of period	$ 22,658	29,540
CDI current period amortization	(1,583)	(1,817)
Total core deposit intangible, end of period	$ 21,075	$ 27,723