Business Combinations, (Bay Bank and Trust Company) (Details) (USD $) Share data in Thousands, unless otherwise specified	12 Months Ended			0 Months Ended	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 16, 2012	Jun. 30, 2012	Mar. 31, 2012
Assets:
Total Assets	$ 0	$ 1,845,543,000	$ 234,960,000
Liabilities:
Total Liabilities	0	1,821,066,000	209,322,000
Bargain purchase gain	0	0	3,635,000
Amortization period of acquired intangible asset	20 years
Bay Bank and Trust Company [Member]
Business Acquisition [Line Items]
Age of acquired entity				76 years
Business acquisition, cost of acquired entity, cash paid				10,000,000
Business acquisition, equity issued (in shares)				510
Business acquisition, equity issued, value assigned				12,000,000
Assets:
Cash and due from banks				88,154,000
Securities available for sale				26,369,000
Acquired noncovered loans				97,914,000
Premises and equipment, net				9,466,000
Identifiable intangible assets				7,017,000
Other real estate				2,569,000
Other assets				3,471,000
Total Assets				234,960,000
Liabilities:
Deposits				208,796,000
Other liabilities				526,000
Total Liabilities				209,322,000
Net assets acquired at fair value				25,638,000
Consideration paid to Bay Bank				22,003,000
Bargain purchase gain				3,635,000	881,000	2,800,000
Income taxes				0
Bargain purchase gain, net of taxes				3,635,000
Business acquisition, total transaction expenses						2,600,000
Business acquisition, severance expense						672,000
Business acquisition, contract termination and other expenses						$ 1,900,000
Amortization period of acquired intangible asset						10 years