Securities (Fair value and gross unrealized losses) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Available-for-sale Securities
Less than 12 months, fair value	$ 422,293	$ 78,022
Less than 12 months, unrealized (losses)	(15,348)	(997)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	422,293	78,022
Total, unrealized (losses)	(15,348)	(997)
Held-to-maturity Securities
Less than 12 months, fair value	141,302	57,572
Less than 12 months, unrealized (losses)	(9,662)	(363)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	141,302	57,572
Total, unrealized (losses)	(9,662)	(363)
U.S. Government agency securities [Member]
Held-to-maturity Securities
Less than 12 months, fair value	139,571	57,572
Less than 12 months, unrealized (losses)	(9,518)	(363)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	139,571	57,572
Total, unrealized (losses)	(9,518)	(363)
Municipal securities [Member]
Held-to-maturity Securities
Less than 12 months, fair value	1,731
Less than 12 months, unrealized (losses)	(144)
12 months or more, fair value	0
12 months or more, unrealized (losses)	0
Total, fair value	1,731
Total, unrealized (losses)	(144)
U.S. Government agency securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	31,003	24,748
Less than 12 months, unrealized (losses)	(2,991)	(252)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	31,003	24,748
Total, unrealized (losses)	(2,991)	(252)
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	67,105
Less than 12 months, unrealized (losses)	(1,844)
12 months or more, fair value	0
12 months or more, unrealized (losses)	0
Total, fair value	67,105
Total, unrealized (losses)	(1,844)
Agency CMOs [Member]
Available-for-sale Securities
Less than 12 months, fair value	298,454	53,274
Less than 12 months, unrealized (losses)	(9,349)	(745)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	298,454	53,274
Total, unrealized (losses)	(9,349)	(745)
Municipal securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	25,731
Less than 12 months, unrealized (losses)	(1,164)
12 months or more, fair value	0
12 months or more, unrealized (losses)	0
Total, fair value	25,731
Total, unrealized (losses)	$ (1,164)