Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset beginning balance	$ 158	$ 215	$ 157	$ 193
Asset, gain (loss) included in earnings	31	(33)	32	(11)
Asset, purchases		0		0
Sales and settlements		0		0
Asset ending balance	189	182	189	182
Transfers out of level 3				0
Interest Rate Lock Commitments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset beginning balance	13,453	5,060	9,161	7,576
Liability beginning balance		683	923	1,222
Asset, gain (loss) included in earnings	53	5,748	4,345	3,232
Liability, gain (loss) included in earnings		496	923	1,035
Sales and settlements	(13,453)		(13,453)
Asset ending balance	53	10,808	53	10,808
Liability ending balance	0	187	0	187
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset beginning balance	89,101	100,384	86,802	91,422
Asset, gain (loss) included in earnings	(417)	1,799	3,157	1,736
Asset, purchases	2,000	5,600	13,775	16,325
Sales and settlements	(675)	(11,300)	(13,725)	(13,000)
Asset ending balance	90,009	96,483	90,009	96,483
Auction Rate Securities Purchase Commitment [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset beginning balance	911		0
Liability beginning balance	142	1,034	1,369	902
Asset, gain (loss) included in earnings	(6)		905
Liability, gain (loss) included in earnings	(134)	557	1,093	425
Asset ending balance	905		905
Liability ending balance	276	477	276	477
Municipal Bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Asset beginning balance	25	62	81	164
Asset, gain (loss) included in earnings	0	3	6	(79)
Sales and settlements	0	0	(62)	(20)
Asset ending balance	$ 25	$ 65	$ 25	$ 65