Acquired Loans - Changes in Accretable Yield of Acquired Loans (Details) - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Change in accretable difference on acquired loans [Abstract]
Accretable yield at beginning of period		$ (52,672)	$ (77,149)	$ (77,149)
Accretion to interest income		14,351	24,907
Disposals		4,306	8,194
Reclassification from nonaccretable difference	[1]	(7,046)	(12,215)
Accretable yield at end of period		$ (41,061)	$ (56,263)	$ (52,672)

[1] Reclassifications from nonaccretable difference are due to lower loss expectations and improvements in expected cash flows.