Bank segment - Contractual maturities of securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Amortized Cost
Due in one year or less	$ 0
Due after one year through five years	29,958
Due after five years through ten years	71,811
Due after ten years	36,824
Total amortized cost	138,593
Mortgage-related securities-FNMA, FHLMC and GNMA - amortized cost	445,559
Total available-for-sale securities, Amortized cost	584,152	549,627
Fair value
Due in one year or less	0
Due after one year through five years	30,296
Due after five years through ten years	73,188
Due after ten years	36,743
Total fair value	140,227
Mortgage-related securities-FNMA, FHLMC and GNMA - fair value	450,421
Available-for-sale securities	$ 590,648	$ 550,394