Fair Value Measurements - Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Interest Rate Lock Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Beginning Balance		$ 9,161
Total Realized and Unrealized Gains (Losses), Assets		4,863
Assets Ending Balance		14,024
Liabilities Beginning Balance		923
Total Realized and Unrealized Gains (Loss), Liabilities		923
Liabilities Ending Balance		0
Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Beginning Balance	$ 158	157
Total Realized and Unrealized Gains (Losses), Assets	6	4
Purchases and Issuances	0	0
Sales and Settlements	0	0
Transfers In (Out)	0	0
Assets Ending Balance	164	161
Auction Rate Securities Purchase Commitment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Beginning Balance	849
Total Realized and Unrealized Gains (Losses), Assets	29
Purchases and Issuances	0
Sales and Settlements	0
Transfers In (Out)	0
Assets Ending Balance	878
Auction rate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Beginning Balance	84,926	86,802
Total Realized and Unrealized Gains (Losses), Assets	642	2,233
Purchases and Issuances	5,000	6,775
Sales and Settlements	(825)	(11,625)
Transfers In (Out)	0
Assets Ending Balance	89,743	84,185
Auction Rate Securities Purchase Commitment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Realized and Unrealized Gains (Losses), Assets		1,540
Assets Ending Balance		1,540
Liabilities Beginning Balance	645	1,369
Total Realized and Unrealized Gains (Loss), Liabilities	286	810
Liabilities Ending Balance	359	559
Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Beginning Balance	44	81
Total Realized and Unrealized Gains (Losses), Assets	(8)	4
Purchases and Issuances	0
Sales and Settlements	0	0
Transfers In (Out)	0
Assets Ending Balance	$ 36	$ 85