Acquisitions - Purchase Price (Details) - Progressive - USD ($) $ in Thousands			12 Months Ended	21 Months Ended
	Apr. 14, 2014		Dec. 31, 2014	Dec. 31, 2015
Business Acquisition [Line Items]
Proceeds from Long-term Debt			$ 491,300
Cash Consideration	$ 185,454
Deferred Cash Consideration	29,106
Purchase Price	705,810	[1]		$ 705,810
Senior Notes | Senior Unsecured Notes, 4.75% Note Due 2017
Business Acquisition [Line Items]
Proceeds from Long-term Debt	300,000
Senior Notes | Senior Unsecured Notes, 3.95% Due 2018
Business Acquisition [Line Items]
Proceeds from Long-term Debt	126,250
Line of Credit | Credit Facility, 2014 | Revolving Credit Agreement
Business Acquisition [Line Items]
Proceeds from Long-term Debt	$ 65,000

[1] As previously reported in the notes to consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2014, which includes the effects of certain measurement period adjustments recognized in 2014.