Bank segment - Components of investment securities (Details) $ in Thousands	Mar. 31, 2017 USD ($) issue	Dec. 31, 2016 USD ($) issue
Available-for-sale securities
Amortized cost	$ 1,241,719	$ 1,118,350
Gross unrealized gains	2,647	2,662
Gross unrealized losses	(15,444)	(15,830)
Available-for-sale investment securities	$ 1,228,922	$ 1,105,182
Available-for-sale Securities, Continuous Unrealized Loss Position
Available-for-sale, securities, less than 12 months, number of issues (in shares) \| issue	110	106
Fair value, less than 12 months	$ 890,244	$ 833,130
Gross unrealized losses, less than 12 months	$ (13,775)	$ (14,153)
Available-for-sale, securities, greater than 12 months, number of issues (in shares) \| issue	14	14
Fair value, 12 months or longer	$ 48,517	$ 50,970
Gross unrealized losses, 12 months or longer	(1,669)	(1,677)
U.S. Treasury and federal agency obligations
Available-for-sale securities
Amortized cost	189,420	193,515
Gross unrealized gains	928	920
Gross unrealized losses	(1,991)	(2,154)
Available-for-sale investment securities	$ 188,357	$ 192,281
Available-for-sale Securities, Continuous Unrealized Loss Position
Available-for-sale, securities, less than 12 months, number of issues (in shares) \| issue	14	18
Fair value, less than 12 months	$ 97,572	$ 123,475
Gross unrealized losses, less than 12 months	$ (1,855)	$ (2,010)
Available-for-sale, securities, greater than 12 months, number of issues (in shares) \| issue	1	1
Fair value, 12 months or longer	$ 3,492	$ 3,485
Gross unrealized losses, 12 months or longer	(136)	(144)
Mortgage-related securities- FNMA, FHLMC and GNMA
Available-for-sale securities
Amortized cost	1,036,872	909,408
Gross unrealized gains	1,719	1,742
Gross unrealized losses	(13,453)	(13,676)
Available-for-sale investment securities	$ 1,025,138	$ 897,474
Available-for-sale Securities, Continuous Unrealized Loss Position
Available-for-sale, securities, less than 12 months, number of issues (in shares) \| issue	96	88
Fair value, less than 12 months	$ 792,672	$ 709,655
Gross unrealized losses, less than 12 months	$ (11,920)	$ (12,143)
Available-for-sale, securities, greater than 12 months, number of issues (in shares) \| issue	13	13
Fair value, 12 months or longer	$ 45,025	$ 47,485
Gross unrealized losses, 12 months or longer	(1,533)	(1,533)
Mortgage revenue bond
Available-for-sale securities
Amortized cost	15,427	15,427
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Available-for-sale investment securities	$ 15,427	$ 15,427
Available-for-sale Securities, Continuous Unrealized Loss Position
Available-for-sale, securities, less than 12 months, number of issues (in shares) \| issue	0	0
Fair value, less than 12 months	$ 0	$ 0
Gross unrealized losses, less than 12 months	$ 0	$ 0
Available-for-sale, securities, greater than 12 months, number of issues (in shares) \| issue	0	0
Fair value, 12 months or longer	$ 0	$ 0
Gross unrealized losses, 12 months or longer	$ 0	$ 0

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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-Publisher FASB
-Name Accounting Standards Codification
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