Loans receivable (Details 6) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Evaluation of impaired loans by portfolio segment and by class of financing receivable
Loans collectively evaluated for impairment	$ 5,728,506	$ 5,691,218
Loans individually evaluated for impairment	122,568	115,073
Loans individually evaluated for impairment for which there is a related impairment reserve	77,998	74,633
Related impairment reserve	17,366	11,903
Loans individually evaluated for impairment for which there is no related impairment reserve	44,570	40,440
Personal Banking
Evaluation of impaired loans by portfolio segment and by class of financing receivable
Loans collectively evaluated for impairment	3,765,865	3,787,814
Loans individually evaluated for impairment	8,856	7,477
Loans individually evaluated for impairment for which there is a related impairment reserve	8,856	7,477
Related impairment reserve	1,604	1,470
Personal Banking | Residential mortgage loans
Evaluation of impaired loans by portfolio segment and by class of financing receivable
Loans collectively evaluated for impairment	2,479,167	2,477,888
Loans individually evaluated for impairment	6,521	5,116
Loans individually evaluated for impairment for which there is a related impairment reserve	6,521	5,116
Related impairment reserve	1,240	1,136
Personal Banking | Home equity loans
Evaluation of impaired loans by portfolio segment and by class of financing receivable
Loans collectively evaluated for impairment	1,063,743	1,081,699
Loans individually evaluated for impairment	2,245	2,240
Loans individually evaluated for impairment for which there is a related impairment reserve	2,245	2,240
Related impairment reserve	347	333
Personal Banking | Other consumer loans
Evaluation of impaired loans by portfolio segment and by class of financing receivable
Loans collectively evaluated for impairment	222,955	228,227
Loans individually evaluated for impairment	90	121
Loans individually evaluated for impairment for which there is a related impairment reserve	90	121
Related impairment reserve	17	1
Business Banking
Evaluation of impaired loans by portfolio segment and by class of financing receivable
Loans collectively evaluated for impairment	1,962,641	1,903,404
Loans individually evaluated for impairment	113,712	107,596
Loans individually evaluated for impairment for which there is a related impairment reserve	69,142	67,156
Related impairment reserve	15,762	10,433
Loans individually evaluated for impairment for which there is no related impairment reserve	44,570	40,440
Business Banking | Commercial real estate loans
Evaluation of impaired loans by portfolio segment and by class of financing receivable
Loans collectively evaluated for impairment	1,577,687	1,532,117
Loans individually evaluated for impairment	86,568	76,282
Loans individually evaluated for impairment for which there is a related impairment reserve	50,176	45,761
Related impairment reserve	8,520	6,300
Loans individually evaluated for impairment for which there is no related impairment reserve	36,392	30,521
Business Banking | Commercial loans
Evaluation of impaired loans by portfolio segment and by class of financing receivable
Loans collectively evaluated for impairment	384,954	371,287
Loans individually evaluated for impairment	27,144	31,314
Loans individually evaluated for impairment for which there is a related impairment reserve	18,966	21,395
Related impairment reserve	7,242	4,133
Loans individually evaluated for impairment for which there is no related impairment reserve	$ 8,178	$ 9,919