FDIC Indemnification Asset (Details) $ in Thousands		3 Months Ended		9 Months Ended
	Aug. 04, 2015 USD ($) acquisition	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)
FDIC Indemnification Asset [Roll Forward]
Balance at the beginning of the period		$ 388	$ 8,887	$ 1,116	$ 4,382
Additions as a result of the Washington Banking Merger		0	0	0	7,174
Cash payments received or receivable from the FDIC		0	(3,102)	(231)	(5,843)
FDIC share of additional estimated (gains) losses		0	(249)	(352)	556
Net amortization		0	(398)	(145)	(1,131)
Change due to termination of FDIC shared-loss agreements		(388)	0	(388)	0
Balance at the end of the period		$ 0	$ 5,138	0	5,138
Number of FDIC-assisted acquisitions | acquisition	3
Consideration paid to FDIC for the termination of shared-loss agreements	$ 7,100
FDIC clawback liability						$ 9,300
Gain on termination of FDIC shared-loss agreements	$ 1,700			$ 1,747	$ 0