Business Combinations - purchased credit impaired loans (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Jul. 17, 2015	Dec. 31, 2014	Oct. 02, 2014
Contractually required principal and interest	$ 332,458		$ 333,880
Non-accretable difference		$ 4,249		$ 7,196
Cash flows expected to be collected		117,248		377,854
Accretable yield		(5,956)		(12,491)
Total purchased credit-impaired loan acquired		111,292		$ 365,363
The Bank shares Inc [Member]
Contractually required principal and interest		12,552
Non-accretable difference		(4,249)
Cash flows expected to be collected		8,303
Accretable yield		(702)
Total purchased credit-impaired loan acquired		111,292
The Bank shares Inc [Member] | Purchased Credit Impaired [Member]
Total purchased credit-impaired loan acquired		$ 7,601