Intangible Assets (Net Carrying Value) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Net carrying value of intangible assets
Goodwill	$ 120,164		$ 120,164	$ 113,414
Other intangible assets:
Total other intangible assets	14,354		15,388	10,607
Core deposit intangible assets [Member]
Other intangible assets:
Total other intangible assets	10,933		11,910	7,144
Mortgage servicing rights [Member]
Other intangible assets:
Total other intangible assets	$ 3,421	$ 3,485	$ 3,478	$ 3,463	$ 3,427	$ 3,593