Acquisitions (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Business Acquisition [Line Items]
Goodwill	$ 46,215
Intangible assets	26,903
Business acquisition, intangible assets amortized period, years	7 years
Intangible assets sold	7,417
Heartland Crop Insurance, Inc [Member]
Business Acquisition [Line Items]
Business acquisition date	Jan. 02, 2011
Business acquisition cash paid	$ 55,000
Premiere Underwriting Services [Member]
Business Acquisition [Line Items]
Business acquisition date	Jan. 28, 2011
Executive Risk Insurance Services, Ltd [Member]
Business Acquisition [Line Items]
Business acquisition date	Jan. 31, 2011