Securities (Fair value and gross unrealized losses) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Available-for-sale Securities
Less than 12 months, fair value	$ 300,598	$ 461,003
Less than 12 months, unrealized (losses)	(11,210)	(21,912)
12 months or more, fair value	107,848	37,423
12 months or more, unrealized (losses)	(7,342)	(4,637)
Total, fair value	408,446	498,426
Total, unrealized (losses)	(18,552)	(26,549)
Held-to-maturity Securities
Less than 12 months, fair value	186,234	211,326
Less than 12 months, unrealized (losses)	(11,420)	(18,293)
12 months or more, fair value	46,093	22,579
12 months or more, unrealized (losses)	(3,907)	(2,421)
Total, fair value	232,327	233,905
Total, unrealized (losses)	(15,327)	(20,714)
U.S. Government agency securities [Member]
Held-to-maturity Securities
Less than 12 months, fair value	90,690	110,435
Less than 12 months, unrealized (losses)	(8,410)	(13,661)
12 months or more, fair value	46,093	22,579
12 months or more, unrealized (losses)	(3,907)	(2,421)
Total, fair value	136,783	133,014
Total, unrealized (losses)	(12,317)	(16,082)
Agency CMOs [Member]
Held-to-maturity Securities
Less than 12 months, fair value	93,749	98,082
Less than 12 months, unrealized (losses)	(2,930)	(4,465)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	93,749	98,082
Total, unrealized (losses)	(2,930)	(4,465)
Municipal securities [Member]
Held-to-maturity Securities
Less than 12 months, fair value	1,795	2,809
Less than 12 months, unrealized (losses)	(80)	(167)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	1,795	2,809
Total, unrealized (losses)	(80)	(167)
U.S. Government agency securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	8,271	8,077
Less than 12 months, unrealized (losses)	(724)	(918)
12 months or more, fair value	22,617	21,849
12 months or more, unrealized (losses)	(2,383)	(3,151)
Total, fair value	30,888	29,926
Total, unrealized (losses)	(3,107)	(4,069)
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	62,400	62,500
Less than 12 months, unrealized (losses)	(2,262)	(3,295)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	62,400	62,500
Total, unrealized (losses)	(2,262)	(3,295)
Agency CMOs [Member]
Available-for-sale Securities
Less than 12 months, fair value	208,601	363,993
Less than 12 months, unrealized (losses)	(7,278)	(16,182)
12 months or more, fair value	85,231	15,574
12 months or more, unrealized (losses)	(4,959)	(1,486)
Total, fair value	293,832	379,567
Total, unrealized (losses)	(12,237)	(17,668)
Municipal securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	21,326	26,433
Less than 12 months, unrealized (losses)	(946)	(1,517)
12 months or more, fair value	0	0
12 months or more, unrealized (losses)	0	0
Total, fair value	21,326	26,433
Total, unrealized (losses)	$ (946)	$ (1,517)