Loans Purchased credit impaired loans (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Purchased credit impaired loans
Outstanding balance of purchased credit impaired loans	$ 24,292	$ 2,277
Carrying amount of purchased credit impaired loans	19,067	1,875
Commercial real estate
Purchased credit impaired loans
Outstanding balance of purchased credit impaired loans	7,762	963
Commercial and industrial
Purchased credit impaired loans
Outstanding balance of purchased credit impaired loans	1,041	78
Residential real estate
Purchased credit impaired loans
Outstanding balance of purchased credit impaired loans	15,183	1,236
Consumer
Purchased credit impaired loans
Outstanding balance of purchased credit impaired loans	$ 306	$ 0