Shareholders' Equity (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($)	Sep. 24, 2013 shares
Equity, Class of Treasury Stock [Line Items]
number of years	2
Dividends declared to shareholders	$ 10,600,000	$ 8,300,000
2012 Common Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, shares of common stock approved for repurchase | shares			250,000
Stock repurchased during period, shares | shares	249,500
Shares repurchased, average cost per share | $ / shares	$ 39.82
The percentage of the stock repurchase program's allotment repurchased during the period	99.80%
Share Repurchase Program, Shares Repurchased as Percentage of Shares Outstanding	2.40%
Subsidiaries [Member]
Equity, Class of Treasury Stock [Line Items]
Dividends declared to shareholders	$ 39,200,000	12,800,000
Acadia Trust [Member]
Equity, Class of Treasury Stock [Line Items]
Dividends declared to shareholders	0	$ 0
SBM Financial, Inc. [Member] | Subsidiaries [Member]
Equity, Class of Treasury Stock [Line Items]
Dividends declared to shareholders	$ 30,000,000