Fair Value Measurement Fair Value Measurement (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Available-for-sale Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
True-up liability, Beginning balance	$ 88,487		$ 126,914		$ 87,539		$ 60,344
(Gains) losses included in earnings	0		0		0		0
Unrealized gains (losses)	1,323	[1]	(2,344)	[1]	3,742	[1]	350	[1]
Purchases	0		20,000		0		83,876
Sales	(40,520)		0		(40,520)		0
Settlements	(1,194)		0		(2,665)		0
Net transfers inton (out of) Level 3	0		0		0		0
True-up liability, Ending balance	48,096		144,570		48,096		144,570
True Up Liability [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
True-up liability, Beginning balance	11,725		11,601		11,551		12,061
(Gains) losses included in earnings	95		595		269		135
Unrealized gains (losses)	0	[1]	0	[1]	0	[1]	0	[1]
Purchases	0		0		0		0
Sales	0		0		0		0
Settlements	0		0		0		0
Net transfers inton (out of) Level 3	0		0		0		0
True-up liability, Ending balance	$ 11,820		$ 12,196		$ 11,820		$ 12,196

[1] Reported in other