Summary of Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Analysis of deferred acquisition costs
Balance, beginning of period	$ 24,421	$ 22,142	$ 16,228
Acquisition costs deferred, net	60,340	54,359	49,399
Costs amortized during the period	(58,579)	(52,080)	(43,044)
Balance, end of period	$ 26,182	$ 24,421	$ 22,142