Fair value measurements (Details 2) - USD ($)	Mar. 31, 2015	Dec. 31, 2014
Fair value measurements on a recurring basis
Available-for-sale securities	$ 590,648,000	$ 550,394,000
Level 1 | Forward sale contracts
Derivative liabilities
Derivative liabilities	0	0
Fair value measurements on a recurring basis | Level 1
Derivative assets
Derivative assets	0	0
Derivative liabilities
Derivative liabilities	249,000	71,000
Fair value measurements on a recurring basis | Level 1 | Forward sale contracts
Derivative assets
Derivative assets	0	0
Derivative liabilities
Derivative liabilities	249,000	71,000
Fair value measurements on a recurring basis | Level 2
Derivative assets
Derivative assets	851,000	398,000
Derivative liabilities
Derivative liabilities	32,000	43,000
Fair value measurements on a recurring basis | Level 2 | Interest rate lock commitments
Derivative assets
Derivative assets	836,000	393,000
Derivative liabilities
Derivative liabilities	1,000	3,000
Fair value measurements on a recurring basis | Level 2 | Forward sale contracts
Derivative assets
Derivative assets	15,000	5,000
Derivative liabilities
Derivative liabilities	31,000	40,000
Fair value measurements on a recurring basis | Level 2 | Bank
Fair value measurements on a recurring basis
Available-for-sale securities	590,648,000	550,394,000
Fair value measurements on a recurring basis | Level 2 | Other
Fair value measurements on a recurring basis
Money market funds	10,000	10,000
Fair value measurements on a recurring basis | Level 2 | Mortgage-related securities - FNMA, FHLMC and GNMA | Bank
Fair value measurements on a recurring basis
Available-for-sale securities	450,421,000	430,834,000
Fair value measurements on a recurring basis | Level 2 | U.S. Treasury federal agency obligations | Bank
Fair value measurements on a recurring basis
Available-for-sale securities	140,227,000	119,560,000
Fair value measurements on a nonrecurring basis | American Savings Bank (ASB)
Derivative liabilities
Adjustments to fair value of loans held for sale	0	0
Fair value measurements on a nonrecurring basis | Level 3
Derivative liabilities
Loans	2,494,000	2,445,000
Real estate acquired in settlement of loans	665,000	288,000
Estimated fair value
Fair value measurements on a recurring basis
Money market funds	10,000	10,000
Available-for-sale securities	590,648,000	550,394,000
Derivative assets
Derivative assets	851,000	398,000
Derivative liabilities
Derivative liabilities	281,000	114,000
Loans	4,616,814,000	4,578,822,000
Estimated fair value | Level 1
Derivative assets
Derivative assets	0	0
Derivative liabilities
Derivative liabilities	249,000	71,000
Estimated fair value | Level 2
Fair value measurements on a recurring basis
Money market funds	10,000	10,000
Available-for-sale securities	590,648,000	550,394,000
Derivative assets
Derivative assets	851,000	398,000
Derivative liabilities
Derivative liabilities	32,000	43,000
Estimated fair value | Level 3
Derivative liabilities
Loans	4,616,814,000	4,578,822,000
Estimated fair value | Fair value measurements on a nonrecurring basis
Derivative liabilities
Loans	2,494,000	2,445,000
Real estate acquired in settlement of loans	$ 665,000	$ 288,000