Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	$ 544	$ 4,402	$ 1,222	$ 3,653
Total Realized and Unrealized Gains (Losses)	(139)	569	539	(180)
Ending Balance	683	3,833	683	3,833
Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	9,149	8,706	9,508	5,946
Total Realized and Unrealized Gains (Losses)	(155)	82	(386)	(87)
Purchases and Issuances	190	115	388	4,167
Sales and Settlements	(70)	(124)	(285)	(627)
Transfers In (Out)	0	0	(111)	(620)
Ending Balance	9,114	8,779	9,114	8,779
Interest Rate Lock Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	11,424	3,038	7,576	2,375
Total Realized and Unrealized Gains (Losses)	(6,364)	7,490	(2,516)	8,153
Ending Balance	5,060	10,528	5,060	10,528
Auction Rate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	99,057	85,025	91,422	85,124
Total Realized and Unrealized Gains (Losses)	(998)	(327)	(63)	(326)
Purchases and Issuances	2,500	10,975	10,725	14,175
Sales and Settlements	(175)	(3,125)	(1,700)	(6,425)
Ending Balance	100,384	92,548	100,384	92,548
Auction Rate Securities Purchase Commitment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	797	2,205	902	2,600
Total Realized and Unrealized Gains (Losses)	(237)	691	(132)	1,086
Ending Balance	1,034	1,514	1,034	1,514
Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	104	70	164	236
Total Realized and Unrealized Gains (Losses)	(22)	(18)	(82)	(184)
Sales and Settlements	(20)		(20)
Ending Balance	$ 62	$ 52	$ 62	$ 52