Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Goodwill and Intangible Assets
Goodwill acquired	$ 114,909			$ 59,630
Mortgage loans serviced	441,000
Peoples Inc Member
Goodwill and Intangible Assets
Goodwill acquired	55,300		$ 55,278
Core Deposits
Goodwill and Intangible Assets
Intangible assets acquired	48,800
Amortization of acquired identifiable intangibles	$ 700	$ 1,400
Core Deposits | Minimum
Goodwill and Intangible Assets
Amortization period	7 years
Core Deposits | Maximum
Goodwill and Intangible Assets
Amortization period	10 years
Core Deposits | Peoples Inc Member
Goodwill and Intangible Assets
Intangible assets acquired	$ 10,500		10,477
Mortgage servicing rights
Goodwill and Intangible Assets
Intangible assets acquired	4,300
Amortization of acquired identifiable intangibles	171
Valuation allowance	$ 0
Mortgage servicing rights | Minimum
Goodwill and Intangible Assets
Discount rate (as a percent)	9.50%
Prepayment speed rate (as a percent)	8.70%
Mortgage servicing rights | Maximum
Goodwill and Intangible Assets
Discount rate (as a percent)	10.50%
Prepayment speed rate (as a percent)	11.30%
Mortgage servicing rights | Peoples Inc Member
Goodwill and Intangible Assets
Intangible assets acquired	$ 4,300		$ 4,301