Securities (Fair value and gross unrealized losses) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Available-for-sale Securities
Less than 12 months, fair value	$ 394,645	$ 78,022
Less than 12 months, unrealized (losses)	(19,122)	(997)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	394,645	78,022
Total, unrealized (losses)	(19,122)	(997)
Held-to-maturity Securities
Less than 12 months, fair value	216,975	57,572
Less than 12 months, unrealized (losses)	(15,786)	(363)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	216,975	57,572
Total, unrealized (losses)	(15,786)	(363)
U.S. Government agency securities [Member]
Held-to-maturity Securities
Less than 12 months, fair value	135,985	57,572
Less than 12 months, unrealized (losses)	(13,108)	(363)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	135,985	57,572
Total, unrealized (losses)	(13,108)	(363)
Agency CMOs [Member]
Held-to-maturity Securities
Less than 12 months, fair value	79,267
Less than 12 months, unrealized (losses)	(2,526)
12 months or more, fair value	0
12 months or more, unrealized (losses)	0
Total, fair value	79,267
Total, unrealized (losses)	(2,526)
Municipal securities [Member]
Held-to-maturity Securities
Less than 12 months, fair value	1,723
Less than 12 months, unrealized (losses)	(152)
12 months or more, fair value	0
12 months or more, unrealized (losses)	0
Total, fair value	1,723
Total, unrealized (losses)	(152)
U.S. Government agency securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	30,372	24,748
Less than 12 months, unrealized (losses)	(3,623)	(252)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	30,372	24,748
Total, unrealized (losses)	(3,623)	(252)
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	61,773
Less than 12 months, unrealized (losses)	(2,274)
12 months or more, fair value	0
12 months or more, unrealized (losses)	0
Total, fair value	61,773
Total, unrealized (losses)	(2,274)
Agency CMOs [Member]
Available-for-sale Securities
Less than 12 months, fair value	276,814	53,274
Less than 12 months, unrealized (losses)	(12,014)	(745)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	276,814	53,274
Total, unrealized (losses)	(12,014)	(745)
Municipal securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	25,686
Less than 12 months, unrealized (losses)	(1,211)
12 months or more, fair value	0
12 months or more, unrealized (losses)	0
Total, fair value	25,686
Total, unrealized (losses)	$ (1,211)