Stockholders' Equity - Reconciliation of Beginning and End of Period Equity Accounts (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Schedule Of Stockholders Equity [Line Items]
Beginning Balance			$ 990,866
Beginning Balance			1,157,625
Balance at December 31, 2013			166,759
Reclassification of redeemable noncontrolling shareholder interest			(152,250)
Net income	38,182	35,486	83,616	91,566
Net income			85,549
Other comprehensive income			8,470
Other comprehensive income	5,126	12,065	7,478	21,197
Dividends payable to noncontrolling shareholders			(2,570)	(9,709)
Stock compensation plans			4,984
Ending Balance	162,195		162,195
Balance at June 30, 2014	42,176		42,176
Cash dividends - $.210 per share			(13,332)
Ending Balance	1,046,300		1,046,300
Ending balance	1,088,476		1,088,476
Noncontrolling Shareholder Interest in Consolidated Subsidiary [Member]
Schedule Of Stockholders Equity [Line Items]
Balance at December 31, 2013			166,759
Reclassification of redeemable noncontrolling shareholder interest			(123,965)
Net income			1,933
Other comprehensive income			19
Dividends payable to noncontrolling shareholders			(2,570)
Balance at June 30, 2014	42,176		42,176
Total Parent Stockholders' Equity [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance			990,866
Reclassification of redeemable noncontrolling shareholder interest			(28,285)
Net income			83,616
Other comprehensive income			8,451
Stock compensation plans			4,984
Cash dividends - $.210 per share			(13,332)
Ending Balance	1,046,300		1,046,300
Redeemable Noncontrolling Shareholder Interest [Member]
Schedule Of Stockholders Equity [Line Items]
Reclassification of redeemable noncontrolling shareholder interest			152,250
Net income			10,937
Other comprehensive income			(992)
Ending Balance	$ 162,195		$ 162,195