Stockholders' Equity (Narrative) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	1 Months Ended	2 Months Ended	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended			108 Months Ended	128 Months Ended
	Feb. 27, 2012	Oct. 31, 2014	Jun. 30, 2004	Dec. 31, 2014	Dec. 31, 2004	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Par Or Stated Value Per Share	$ 0.01			$ 0.01			$ 0.01	$ 0.01		$ 0.01	$ 0.01
Assumed forfeiture rate				0.00%			0.00%				0.00%
Options outstanding, shares				37,000			37,000				37,000
Sale of Common Stock, shares	12,000,000
Sale of Common Stock, price per share	$ 30.83
Proceeds from sale of Common Stock									$ 369,584
Underwriting discounts and estimated transaction expenses payable									376
Repurchase of common stock			39,865,266		39,865,266					39,865,266	40,032,366
Aggregate cost of common stock repurchase			784,040		784,040		7,317		18,597	784,040	791,357
Common stock repurchased in the period								0
Payments for repurchase of common stock							7,317	0	18,597
Cash dividend per share				$ 0.13		$ 0.115	$ 0.475	$ 0.415	$ 0.37
Cash dividend per common share, increase		$ 0.015
Cash dividends on common stock							58,906	51,213	44,465
Repurchase of common stock, maximum value				1,200,000			1,200,000				1,200,000
Remaining value of common stock authorized under repurchase program				408,643			408,643				408,643
Common stock, shares authorized but unissued				126,015,473			126,015,473				126,015,473
Aggregate intrinsic value for options exercisable				1,056			1,056				1,056
Aggregate intrinsic value for options outstanding				1,056			1,056				1,056
Total intrinsic value of stock options exercised							$ 7,458	$ 5,729	$ 6,239
Exercisable options to purchase common stock				37,000			37,000	274,902	484,794	274,902	37,000
2014 Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance				3,250,000			3,250,000				3,250,000
2004 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of award								$ 34.06	$ 31.52
Common stock reserved for issuance				7,162,500			7,162,500				7,162,500
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant expiration							2015
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrant expiration							2019
Maximum [Member] | 2014 Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award term							10 years
Maximum [Member] | 2004 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award term							5 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of award							$ 42.54
Vested deferred RSUs outstanding				223,752			223,752	163,995	102,477	163,995	223,752
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of award							$ 42.33
Vesting period of award							3 years
Performance period end date							Dec. 31, 2016