Fair Value Measurements (Carrying Amounts and Estimated Fair Values of Financial Instruments Not Measured at Fair Value) (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Carrying Amount
Assets:
Cash and cash equivalents	$ 1,141,915	$ 1,006,138
Deposits with banks	20,940	21,222
Notes receivable, net	7,466	7,799
Liabilities:
Deposits	2,965,426	2,779,478
Notes and contracts payable	734,091	736,693
Estimated Fair Value
Assets:
Cash and cash equivalents	1,141,915	1,006,138
Deposits with banks	20,887	21,176
Notes receivable, net	7,297	7,542
Liabilities:
Deposits	2,965,426	2,779,478
Notes and contracts payable	756,536	734,812
Estimated Fair Value | Level 1
Assets:
Cash and cash equivalents	1,141,915	1,006,138
Deposits with banks	265	1,017
Notes receivable, net	0	0
Liabilities:
Deposits	2,965,426	2,779,478
Notes and contracts payable	0	0
Estimated Fair Value | Level 2
Assets:
Cash and cash equivalents	0	0
Deposits with banks	20,622	20,159
Notes receivable, net	0	0
Liabilities:
Deposits	0	0
Notes and contracts payable	752,070	729,658
Estimated Fair Value | Level 3
Assets:
Cash and cash equivalents	0	0
Deposits with banks	0	0
Notes receivable, net	7,297	7,542
Liabilities:
Deposits	0	0
Notes and contracts payable	$ 4,466	$ 5,154